Chapter 5 MySQL Server Administration

Table of Contents

5.1 The MySQL Server
5.1.1 Server Option and Variable Reference
5.1.2 Server Configuration Defaults
5.1.3 Server Command Options
5.1.4 Server System Variables
5.1.5 Using System Variables
5.1.6 Server Status Variables
5.1.7 Server SQL Modes
5.1.8 Server Plugins
5.1.9 IPv6 Support
5.1.10 Server-Side Help
5.1.11 Server Response to Signals
5.1.12 The Shutdown Process
5.2 MySQL Server Logs
5.2.1 Selecting General Query and Slow Query Log Output Destinations
5.2.2 The Error Log
5.2.3 The General Query Log
5.2.4 The Binary Log
5.2.5 The Slow Query Log
5.2.6 The DDL Log
5.2.7 Server Log Maintenance
5.3 Running Multiple MySQL Instances on One Machine
5.3.1 Setting Up Multiple Data Directories
5.3.2 Running Multiple MySQL Instances on Windows
5.3.3 Running Multiple MySQL Instances on Unix
5.3.4 Using Client Programs in a Multiple-Server Environment
5.4 Tracing mysqld Using DTrace
5.4.1 mysqld DTrace Probe Reference

MySQL Server (mysqld) is the main program that does most of the work in a MySQL installation. This chapter provides an overview of MySQL Server and covers general server administration:

For additional information on administrative topics, see also:

5.1 The MySQL Server

mysqld is the MySQL server. The following discussion covers these MySQL server configuration topics:

  • Startup options that the server supports. You can specify these options on the command line, through configuration files, or both.

  • Server system variables. These variables reflect the current state and values of the startup options, some of which can be modified while the server is running.

  • Server status variables. These variables contain counters and statistics about runtime operation.

  • How to set the server SQL mode. This setting modifies certain aspects of SQL syntax and semantics, for example for compatibility with code from other database systems, or to control the error handling for particular situations.

  • The server shutdown process. There are performance and reliability considerations depending on the type of table (transactional or nontransactional) and whether you use replication.

Note

Not all storage engines are supported by all MySQL server binaries and configurations. To find out how to determine which storage engines your MySQL server installation supports, see Section 13.7.5.17, “SHOW ENGINES Syntax”.

5.1.1 Server Option and Variable Reference

The following table provides a list of all the command line options, server and status variables applicable within mysqld.

The table lists command-line options (Cmd-line), options valid in configuration files (Option file), server system variables (System Var), and status variables (Status var) in one unified list, with notification of where each option/variable is valid. If a server option set on the command line or in an option file differs from the name of the corresponding server system or status variable, the variable name is noted immediately below the corresponding option. For status variables, the scope of the variable is shown (Scope) as either global, session, or both. Please see the corresponding sections for details on setting and using the options and variables. Where appropriate, a direct link to further information on the item as available.

For a version of this table that is specific to MySQL Cluster, see Section 18.3.4.1, “MySQL Cluster mysqld Option and Variable Reference”.

Table 5.1 Option/Variable Summary

NameCmd-LineOption FileSystem VarStatus VarVar ScopeDynamic
abort-slave-event-countYesYes    
Aborted_clients   YesGlobalNo
Aborted_connects   YesGlobalNo
allow-suspicious-udfsYesYes    
ansiYesYes    
audit-logYesYes    
audit_log_buffer_sizeYesYesYes GlobalNo
audit_log_connection_policyYesYesYes GlobalYes
audit_log_current_session  Yes BothNo
Audit_log_current_size   YesGlobalNo
Audit_log_event_max_drop_size   YesGlobalNo
Audit_log_events   YesGlobalNo
Audit_log_events_filtered   YesGlobalNo
Audit_log_events_lost   YesGlobalNo
Audit_log_events_written   YesGlobalNo
audit_log_exclude_accountsYesYesYes GlobalYes
audit_log_fileYesYesYes GlobalNo
audit_log_flush  Yes GlobalYes
audit_log_formatYesYesYes GlobalNo
audit_log_include_accountsYesYesYes GlobalYes
audit_log_policyYesYesYes GlobalVaries
audit_log_rotate_on_sizeYesYesYes GlobalYes
audit_log_statement_policyYesYesYes GlobalYes
audit_log_strategyYesYesYes GlobalNo
Audit_log_total_size   YesGlobalNo
Audit_log_write_waits   YesGlobalNo
authentication_windows_log_levelYesYes    
authentication_windows_use_principal_nameYesYes    
auto_increment_increment  Yes BothYes
auto_increment_offset  Yes BothYes
autocommitYesYesYes BothYes
automatic_sp_privileges  Yes GlobalYes
back_log  Yes GlobalNo
basedirYesYesYes GlobalNo
big-tablesYesYes  BothYes
- Variable: big_tables  Yes BothYes
bind-addressYesYes  GlobalNo
- Variable: bind_address  Yes GlobalNo
Binlog_cache_disk_use   YesGlobalNo
binlog_cache_sizeYesYesYes GlobalYes
Binlog_cache_use   YesGlobalNo
binlog-checksumYesYes    
binlog_checksum  Yes GlobalYes
binlog_direct_non_transactional_updatesYesYesYes BothYes
binlog-do-dbYesYes    
binlog_error_actionYesYesYes BothYes
binlog-formatYesYes  BothYes
- Variable: binlog_format  Yes BothYes
binlog_gtid_recovery_simplifiedYesYesYes GlobalNo
binlog-ignore-dbYesYes    
binlog_max_flush_queue_time  Yes GlobalYes
binlog_order_commits  Yes GlobalYes
binlog-row-event-max-sizeYesYes    
binlog_row_imageYesYesYes BothYes
binlog_rows_query_log_events  Yes BothYes
binlog-rows-query-log-eventsYesYes    
- Variable: binlog_rows_query_log_events      
Binlog_stmt_cache_disk_use   YesGlobalNo
binlog_stmt_cache_sizeYesYesYes GlobalYes
Binlog_stmt_cache_use   YesGlobalNo
binlogging_impossible_modeYesYesYes BothYes
block_encryption_modeYesYesYes BothYes
bootstrapYesYes    
bulk_insert_buffer_sizeYesYesYes BothYes
Bytes_received   YesBothNo
Bytes_sent   YesBothNo
character_set_client  Yes BothYes
character-set-client-handshakeYesYes    
character_set_connection  Yes BothYes
character_set_database[a]  Yes BothYes
character-set-filesystemYesYes  BothYes
- Variable: character_set_filesystem  Yes BothYes
character_set_results  Yes BothYes
character-set-serverYesYes  BothYes
- Variable: character_set_server  Yes BothYes
character_set_system  Yes GlobalNo
character-sets-dirYesYes  GlobalNo
- Variable: character_sets_dir  Yes GlobalNo
chrootYesYes    
collation_connection  Yes BothYes
collation_database[b]  Yes BothYes
collation-serverYesYes  BothYes
- Variable: collation_server  Yes BothYes
Com_admin_commands   YesBothNo
Com_alter_db   YesBothNo
Com_alter_db_upgrade   YesBothNo
Com_alter_event   YesBothNo
Com_alter_function   YesBothNo
Com_alter_procedure   YesBothNo
Com_alter_server   YesBothNo
Com_alter_table   YesBothNo
Com_alter_tablespace   YesBothNo
Com_alter_user   YesBothNo
Com_analyze   YesBothNo
Com_assign_to_keycache   YesBothNo
Com_begin   YesBothNo
Com_binlog   YesBothNo
Com_call_procedure   YesBothNo
Com_change_db   YesBothNo
Com_change_master   YesBothNo
Com_check   YesBothNo
Com_checksum   YesBothNo
Com_commit   YesBothNo
Com_create_db   YesBothNo
Com_create_event   YesBothNo
Com_create_function   YesBothNo
Com_create_index   YesBothNo
Com_create_procedure   YesBothNo
Com_create_server   YesBothNo
Com_create_table   YesBothNo
Com_create_trigger   YesBothNo
Com_create_udf   YesBothNo
Com_create_user   YesBothNo
Com_create_view   YesBothNo
Com_dealloc_sql   YesBothNo
Com_delete   YesBothNo
Com_delete_multi   YesBothNo
Com_do   YesBothNo
Com_drop_db   YesBothNo
Com_drop_event   YesBothNo
Com_drop_function   YesBothNo
Com_drop_index   YesBothNo
Com_drop_procedure   YesBothNo
Com_drop_server   YesBothNo
Com_drop_table   YesBothNo
Com_drop_trigger   YesBothNo
Com_drop_user   YesBothNo
Com_drop_view   YesBothNo
Com_empty_query   YesBothNo
Com_execute_sql   YesBothNo
Com_flush   YesBothNo
Com_get_diagnostics   YesBothNo
Com_grant   YesBothNo
Com_ha_close   YesBothNo
Com_ha_open   YesBothNo
Com_ha_read   YesBothNo
Com_help   YesBothNo
Com_insert   YesBothNo
Com_insert_select   YesBothNo
Com_install_plugin   YesBothNo
Com_kill   YesBothNo
Com_load   YesBothNo
Com_lock_tables   YesBothNo
Com_optimize   YesBothNo
Com_preload_keys   YesBothNo
Com_prepare_sql   YesBothNo
Com_purge   YesBothNo
Com_purge_before_date   YesBothNo
Com_release_savepoint   YesBothNo
Com_rename_table   YesBothNo
Com_rename_user   YesBothNo
Com_repair   YesBothNo
Com_replace   YesBothNo
Com_replace_select   YesBothNo
Com_reset   YesBothNo
Com_resignal   YesBothNo
Com_revoke   YesBothNo
Com_revoke_all   YesBothNo
Com_rollback   YesBothNo
Com_rollback_to_savepoint   YesBothNo
Com_savepoint   YesBothNo
Com_select   YesBothNo
Com_set_option   YesBothNo
Com_show_authors   YesBothNo
Com_show_binlog_events   YesBothNo
Com_show_binlogs   YesBothNo
Com_show_charsets   YesBothNo
Com_show_collations   YesBothNo
Com_show_contributors   YesBothNo
Com_show_create_db   YesBothNo
Com_show_create_event   YesBothNo
Com_show_create_func   YesBothNo
Com_show_create_proc   YesBothNo
Com_show_create_table   YesBothNo
Com_show_create_trigger   YesBothNo
Com_show_databases   YesBothNo
Com_show_engine_logs   YesBothNo
Com_show_engine_mutex   YesBothNo
Com_show_engine_status   YesBothNo
Com_show_errors   YesBothNo
Com_show_events   YesBothNo
Com_show_fields   YesBothNo
Com_show_function_code   YesBothNo
Com_show_function_status   YesBothNo
Com_show_grants   YesBothNo
Com_show_keys   YesBothNo
Com_show_master_status   YesBothNo
Com_show_ndb_status   YesBothNo
Com_show_new_master   YesBothNo
Com_show_open_tables   YesBothNo
Com_show_plugins   YesBothNo
Com_show_privileges   YesBothNo
Com_show_procedure_code   YesBothNo
Com_show_procedure_status   YesBothNo
Com_show_processlist   YesBothNo
Com_show_profile   YesBothNo
Com_show_profiles   YesBothNo
Com_show_relaylog_events   YesBothNo
Com_show_slave_hosts   YesBothNo
Com_show_slave_status   YesBothNo
Com_show_status   YesBothNo
Com_show_storage_engines   YesBothNo
Com_show_table_status   YesBothNo
Com_show_tables   YesBothNo
Com_show_triggers   YesBothNo
Com_show_variables   YesBothNo
Com_show_warnings   YesBothNo
Com_signal   YesBothNo
Com_slave_start   YesBothNo
Com_slave_stop   YesBothNo
Com_stmt_close   YesBothNo
Com_stmt_execute   YesBothNo
Com_stmt_fetch   YesBothNo
Com_stmt_prepare   YesBothNo
Com_stmt_reprepare   YesBothNo
Com_stmt_reset   YesBothNo
Com_stmt_send_long_data   YesBothNo
Com_truncate   YesBothNo
Com_uninstall_plugin   YesBothNo
Com_unlock_tables   YesBothNo
Com_update   YesBothNo
Com_update_multi   YesBothNo
Com_xa_commit   YesBothNo
Com_xa_end   YesBothNo
Com_xa_prepare   YesBothNo
Com_xa_recover   YesBothNo
Com_xa_rollback   YesBothNo
Com_xa_start   YesBothNo
completion_typeYesYesYes BothYes
Compression   YesSessionNo
concurrent_insertYesYesYes GlobalYes
connect_timeoutYesYesYes GlobalYes
Connection_errors_accept   YesGlobalNo
Connection_errors_internal   YesGlobalNo
Connection_errors_max_connections   YesGlobalNo
Connection_errors_peer_addr   YesGlobalNo
Connection_errors_select   YesGlobalNo
Connection_errors_tcpwrap   YesGlobalNo
Connections   YesGlobalNo
consoleYesYes    
core_file  Yes GlobalNo
core-fileYesYes    
Created_tmp_disk_tables   YesBothNo
Created_tmp_files   YesGlobalNo
Created_tmp_tables   YesBothNo
daemon_memcached_enable_binlogYesYesYes GlobalNo
daemon_memcached_engine_lib_nameYesYesYes GlobalNo
daemon_memcached_engine_lib_pathYesYesYes GlobalNo
daemon_memcached_optionYesYesYes GlobalNo
daemon_memcached_r_batch_sizeYesYesYes GlobalNo
daemon_memcached_w_batch_sizeYesYesYes GlobalNo
datadirYesYesYes GlobalNo
date_format  Yes GlobalNo
datetime_format  Yes GlobalNo
debugYesYesYes BothYes
debug_sync  Yes SessionYes
debug-sync-timeoutYesYes    
default-authentication-pluginYesYes    
default-storage-engineYesYes  BothYes
- Variable: default_storage_engine  Yes BothYes
default-time-zoneYesYes    
default_tmp_storage_engineYesYesYes BothYes
default_week_formatYesYesYes BothYes
defaults-extra-fileYes     
defaults-fileYes     
defaults-group-suffixYes     
delay-key-writeYesYes  GlobalYes
- Variable: delay_key_write  Yes GlobalYes
Delayed_errors   YesGlobalNo
delayed_insert_limitYesYesYes GlobalYes
Delayed_insert_threads   YesGlobalNo
delayed_insert_timeoutYesYesYes GlobalYes
delayed_queue_sizeYesYesYes GlobalYes
Delayed_writes   YesGlobalNo
des-key-fileYesYes    
disable_gtid_unsafe_statementsYesYesYes GlobalNo
disable-gtid-unsafe-statementsYesYesYes GlobalNo
disconnect_on_expired_passwordYesYesYes SessionNo
disconnect-slave-event-countYesYes    
div_precision_incrementYesYesYes BothYes
enable-named-pipeYesYes    
- Variable: named_pipe      
end_markers_in_json  Yes BothYes
enforce_gtid_consistencyYesYesYes GlobalNo
enforce-gtid-consistencyYesYesYes GlobalNo
engine-condition-pushdownYesYes  BothYes
- Variable: engine_condition_pushdown  Yes BothYes
eq_range_index_dive_limit  Yes BothYes
error_count  Yes SessionNo
event-schedulerYesYes  GlobalYes
- Variable: event_scheduler  Yes GlobalYes
exit-infoYesYes    
expire_logs_daysYesYesYes GlobalYes
explicit_defaults_for_timestampYesYesYes SessionNo
external-lockingYesYes    
- Variable: skip_external_locking      
external_user  Yes SessionNo
federatedYesYes    
flushYesYesYes GlobalYes
Flush_commands   YesGlobalNo
flush_timeYesYesYes GlobalYes
foreign_key_checks  Yes BothYes
ft_boolean_syntaxYesYesYes GlobalYes
ft_max_word_lenYesYesYes GlobalNo
ft_min_word_lenYesYesYes GlobalNo
ft_query_expansion_limitYesYesYes GlobalNo
ft_stopword_fileYesYesYes GlobalNo
gdbYesYes    
general-logYesYes  GlobalYes
- Variable: general_log  Yes GlobalYes
general_log_fileYesYesYes GlobalYes
group_concat_max_lenYesYesYes BothYes
gtid_done  Yes BothNo
gtid_executed  Yes BothNo
gtid_lost  Yes GlobalNo
gtid_mode  Yes GlobalNo
gtid-modeYesYes  GlobalNo
- Variable: gtid_mode  Yes GlobalNo
gtid_next  Yes SessionYes
gtid_owned  Yes BothNo
gtid_purged  Yes GlobalYes
Handler_commit   YesBothNo
Handler_delete   YesBothNo
Handler_discover   YesBothNo
Handler_external_lock   YesBothNo
Handler_mrr_init   YesBothNo
Handler_prepare   YesBothNo
Handler_read_first   YesBothNo
Handler_read_key   YesBothNo
Handler_read_last   YesBothNo
Handler_read_next   YesBothNo
Handler_read_prev   YesBothNo
Handler_read_rnd   YesBothNo
Handler_read_rnd_next   YesBothNo
Handler_rollback   YesBothNo
Handler_savepoint   YesBothNo
Handler_savepoint_rollback   YesBothNo
Handler_update   YesBothNo
Handler_write   YesBothNo
have_compress  Yes GlobalNo
have_crypt  Yes GlobalNo
have_csv  Yes GlobalNo
have_dynamic_loading  Yes GlobalNo
have_geometry  Yes GlobalNo
have_innodb  Yes GlobalNo
have_ndbcluster  Yes GlobalNo
have_openssl  Yes GlobalNo
have_partitioning  Yes GlobalNo
have_profiling  Yes GlobalNo
have_query_cache  Yes GlobalNo
have_rtree_keys  Yes GlobalNo
have_ssl  Yes GlobalNo
have_symlink  Yes GlobalNo
helpYesYes    
host_cache_size  Yes GlobalYes
hostname  Yes GlobalNo
identity  Yes SessionYes
ignore-builtin-innodbYesYes  GlobalNo
- Variable: ignore_builtin_innodb  Yes GlobalNo
ignore-db-dirYesYes    
ignore_db_dirs  Yes GlobalNo
init_connectYesYesYes GlobalYes
init-fileYesYes  GlobalNo
- Variable: init_file  Yes GlobalNo
init_slaveYesYesYes GlobalYes
innodbYesYes    
innodb_adaptive_flushingYesYesYes GlobalYes
innodb_adaptive_flushing_lwmYesYesYes GlobalYes
innodb_adaptive_hash_indexYesYesYes GlobalYes
innodb_adaptive_max_sleep_delayYesYesYes GlobalYes
innodb_additional_mem_pool_sizeYesYesYes GlobalNo
innodb_api_bk_commit_intervalYesYesYes GlobalYes
innodb_api_disable_rowlockYesYesYes GlobalNo
innodb_api_enable_binlogYesYesYes GlobalNo
innodb_api_enable_mdlYesYesYes GlobalNo
innodb_api_trx_levelYesYesYes GlobalYes
innodb_autoextend_incrementYesYesYes GlobalYes
innodb_autoinc_lock_modeYesYesYes GlobalNo
Innodb_available_undo_logs   YesGlobalNo
Innodb_buffer_pool_bytes_data   YesGlobalNo
Innodb_buffer_pool_bytes_dirty   YesGlobalNo
innodb_buffer_pool_dump_at_shutdownYesYesYes GlobalYes
innodb_buffer_pool_dump_nowYesYesYes GlobalYes
Innodb_buffer_pool_dump_status   YesGlobalNo
innodb_buffer_pool_filenameYesYesYes GlobalYes
innodb_buffer_pool_instancesYesYesYes GlobalNo
innodb_buffer_pool_load_abortYesYesYes GlobalYes
innodb_buffer_pool_load_at_startupYesYesYes GlobalNo
innodb_buffer_pool_load_nowYesYesYes GlobalYes
Innodb_buffer_pool_load_status   YesGlobalNo
Innodb_buffer_pool_pages_data   YesGlobalNo
Innodb_buffer_pool_pages_dirty   YesGlobalNo
Innodb_buffer_pool_pages_flushed   YesGlobalNo
Innodb_buffer_pool_pages_free   YesGlobalNo
Innodb_buffer_pool_pages_latched   YesGlobalNo
Innodb_buffer_pool_pages_misc   YesGlobalNo
Innodb_buffer_pool_pages_total   YesGlobalNo
Innodb_buffer_pool_read_ahead   YesGlobalNo
Innodb_buffer_pool_read_ahead_evicted   YesGlobalNo
Innodb_buffer_pool_read_requests   YesGlobalNo
Innodb_buffer_pool_reads   YesGlobalNo
innodb_buffer_pool_sizeYesYesYes GlobalNo
Innodb_buffer_pool_wait_free   YesGlobalNo
Innodb_buffer_pool_write_requests   YesGlobalNo
innodb_change_buffer_max_sizeYesYesYes GlobalYes
innodb_change_bufferingYesYesYes GlobalYes
innodb_checksum_algorithmYesYesYes GlobalYes
innodb_checksumsYesYesYes GlobalNo
innodb_cmp_per_index_enabledYesYesYes GlobalYes
innodb_commit_concurrencyYesYesYes GlobalYes
innodb_compression_failure_threshold_pctYesYesYes GlobalYes
innodb_compression_levelYesYesYes GlobalYes
innodb_compression_pad_pct_maxYesYesYes GlobalYes
innodb_concurrency_ticketsYesYesYes GlobalYes
innodb_data_file_pathYesYesYes GlobalNo
Innodb_data_fsyncs   YesGlobalNo
innodb_data_home_dirYesYesYes GlobalNo
Innodb_data_pending_fsyncs   YesGlobalNo
Innodb_data_pending_reads   YesGlobalNo
Innodb_data_pending_writes   YesGlobalNo
Innodb_data_read   YesGlobalNo
Innodb_data_reads   YesGlobalNo
Innodb_data_writes   YesGlobalNo
Innodb_data_written   YesGlobalNo
Innodb_dblwr_pages_written   YesGlobalNo
Innodb_dblwr_writes   YesGlobalNo
innodb_disable_sort_file_cacheYesYesYes GlobalYes
innodb_doublewriteYesYesYes GlobalNo
innodb_fast_shutdownYesYesYes GlobalYes
innodb_file_formatYesYesYes GlobalYes
innodb_file_format_checkYesYesYes GlobalNo
innodb_file_format_maxYesYesYes GlobalYes
innodb_file_per_tableYesYesYes GlobalYes
innodb_flush_log_at_timeout  Yes GlobalYes
innodb_flush_log_at_trx_commitYesYesYes GlobalYes
innodb_flush_methodYesYesYes GlobalNo
innodb_flush_neighborsYesYesYes GlobalYes
innodb_flushing_avg_loopsYesYesYes GlobalYes
innodb_force_load_corruptedYesYesYes GlobalNo
innodb_force_recoveryYesYesYes GlobalNo
innodb_ft_aux_table  Yes GlobalYes
innodb_ft_cache_sizeYesYesYes GlobalNo
innodb_ft_enable_diag_printYesYesYes GlobalYes
innodb_ft_enable_stopwordYesYesYes GlobalYes
innodb_ft_max_token_sizeYesYesYes GlobalNo
innodb_ft_min_token_sizeYesYesYes GlobalNo
innodb_ft_num_word_optimizeYesYesYes GlobalYes
innodb_ft_result_cache_limitYesYesYes GlobalYes
innodb_ft_server_stopword_tableYesYesYes GlobalYes
innodb_ft_sort_pll_degreeYesYesYes GlobalNo
innodb_ft_total_cache_sizeYesYesYes GlobalNo
innodb_ft_user_stopword_tableYesYesYes BothYes
Innodb_have_atomic_builtins   YesGlobalNo
innodb_io_capacityYesYesYes GlobalYes
innodb_io_capacity_maxYesYesYes GlobalYes
innodb_large_prefixYesYesYes GlobalYes
innodb_lock_wait_timeoutYesYesYes BothYes
innodb_locks_unsafe_for_binlogYesYesYes GlobalNo
innodb_log_buffer_sizeYesYesYes GlobalNo
innodb_log_compressed_pagesYesYesYes GlobalYes
innodb_log_file_sizeYesYesYes GlobalNo
innodb_log_files_in_groupYesYesYes GlobalNo
innodb_log_group_home_dirYesYesYes GlobalNo
Innodb_log_waits   YesGlobalNo
Innodb_log_write_requests   YesGlobalNo
Innodb_log_writes   YesGlobalNo
innodb_lru_scan_depthYesYesYes GlobalYes
innodb_max_dirty_pages_pctYesYesYes GlobalYes
innodb_max_dirty_pages_pct_lwmYesYesYes GlobalYes
innodb_max_purge_lagYesYesYes GlobalYes
innodb_max_purge_lag_delayYesYesYes GlobalYes
innodb_mirrored_log_groupsYesYesYes GlobalNo
innodb_monitor_disableYesYesYes GlobalYes
innodb_monitor_enableYesYesYes GlobalYes
innodb_monitor_resetYesYesYes GlobalYes
innodb_monitor_reset_allYesYesYes GlobalYes
Innodb_num_open_files   YesGlobalNo
innodb_old_blocks_pctYesYesYes GlobalYes
innodb_old_blocks_timeYesYesYes GlobalYes
innodb_online_alter_log_max_sizeYesYesYes GlobalYes
innodb_open_filesYesYesYes GlobalNo
innodb_optimize_fulltext_onlyYesYesYes GlobalYes
Innodb_os_log_fsyncs   YesGlobalNo
Innodb_os_log_pending_fsyncs   YesGlobalNo
Innodb_os_log_pending_writes   YesGlobalNo
Innodb_os_log_written   YesGlobalNo
innodb_page_sizeYesYesYes GlobalNo
Innodb_page_size   YesGlobalNo
Innodb_pages_created   YesGlobalNo
Innodb_pages_read   YesGlobalNo
Innodb_pages_written   YesGlobalNo
innodb_print_all_deadlocksYesYesYes GlobalYes
innodb_purge_batch_sizeYesYesYes GlobalYes
innodb_purge_threadsYesYesYes GlobalNo
innodb_random_read_aheadYesYesYes GlobalYes
innodb_read_ahead_thresholdYesYesYes GlobalYes
innodb_read_io_threadsYesYesYes GlobalNo
innodb_read_onlyYesYesYes GlobalNo
innodb_replication_delayYesYesYes GlobalYes
innodb_rollback_on_timeoutYesYesYes GlobalNo
innodb_rollback_segmentsYesYesYes GlobalYes
Innodb_row_lock_current_waits   YesGlobalNo
Innodb_row_lock_time   YesGlobalNo
Innodb_row_lock_time_avg   YesGlobalNo
Innodb_row_lock_time_max   YesGlobalNo
Innodb_row_lock_waits   YesGlobalNo
Innodb_rows_deleted   YesGlobalNo
Innodb_rows_inserted   YesGlobalNo
Innodb_rows_read   YesGlobalNo
Innodb_rows_updated   YesGlobalNo
innodb_sort_buffer_sizeYesYesYes GlobalNo
innodb_spin_wait_delayYesYesYes GlobalYes
innodb_stats_auto_recalcYesYesYes GlobalYes
innodb_stats_methodYesYesYes GlobalYes
innodb_stats_on_metadataYesYesYes GlobalYes
innodb_stats_persistentYesYesYes GlobalYes
innodb_stats_persistent_sample_pagesYesYesYes GlobalYes
innodb_stats_sample_pagesYesYesYes GlobalYes
innodb_stats_transient_sample_pagesYesYesYes GlobalYes
innodb-status-fileYesYes    
innodb_status_outputYesYesYes GlobalYes
innodb_status_output_locksYesYesYes GlobalYes
innodb_strict_modeYesYesYes BothYes
innodb_support_xaYesYesYes BothYes
innodb_sync_array_sizeYesYesYes GlobalNo
innodb_sync_spin_loopsYesYesYes GlobalYes
innodb_table_locksYesYesYes BothYes
innodb_thread_concurrencyYesYesYes GlobalYes
innodb_thread_sleep_delayYesYesYes GlobalYes
Innodb_truncated_status_writes   YesGlobalNo
innodb_undo_directoryYesYesYes GlobalNo
innodb_undo_logsYesYesYes GlobalYes
innodb_undo_tablespacesYesYesYes GlobalNo
innodb_use_native_aioYesYesYes GlobalNo
innodb_use_sys_mallocYesYesYes GlobalNo
innodb_version  Yes GlobalNo
innodb_write_io_threadsYesYesYes GlobalNo
insert_id  Yes SessionYes
installYes     
install-manualYes     
interactive_timeoutYesYesYes BothYes
join_buffer_sizeYesYesYes BothYes
keep_files_on_createYesYesYes BothYes
Key_blocks_not_flushed   YesGlobalNo
Key_blocks_unused   YesGlobalNo
Key_blocks_used   YesGlobalNo
key_buffer_sizeYesYesYes GlobalYes
key_cache_age_thresholdYesYesYes GlobalYes
key_cache_block_sizeYesYesYes GlobalYes
key_cache_division_limitYesYesYes GlobalYes
Key_read_requests   YesGlobalNo
Key_reads   YesGlobalNo
Key_write_requests   YesGlobalNo
Key_writes   YesGlobalNo
languageYesYesYes GlobalNo
large_files_support  Yes GlobalNo
large_page_size  Yes GlobalNo
large-pagesYesYes  GlobalNo
- Variable: large_pages  Yes GlobalNo
last_insert_id  Yes SessionYes
Last_query_cost   YesSessionNo
Last_query_partial_plans   YesSessionNo
lc-messagesYesYes  BothYes
- Variable: lc_messages  Yes BothYes
lc-messages-dirYesYes  GlobalNo
- Variable: lc_messages_dir  Yes GlobalNo
lc_time_names  Yes BothYes
license  Yes GlobalNo
local_infile  Yes GlobalYes
local-serviceYes     
lock_wait_timeoutYesYesYes BothYes
locked_in_memory  Yes GlobalNo
logYesYesYes GlobalYes
log_bin  Yes GlobalNo
log-binYesYesYes GlobalNo
log_bin_basename  Yes GlobalNo
log_bin_index  Yes GlobalNo
log-bin-indexYesYes    
log-bin-trust-function-creatorsYesYes  GlobalYes
- Variable: log_bin_trust_function_creators  Yes GlobalYes
log_bin_use_v1_row_eventsYesYesYes GlobalNo
log-bin-use-v1-row-eventsYesYes  GlobalNo
- Variable: log_bin_use_v1_row_events  Yes GlobalNo
log-errorYesYes  GlobalNo
- Variable: log_error  Yes GlobalNo
log-isamYesYes    
log-outputYesYes  GlobalYes
- Variable: log_output  Yes GlobalYes
log-queries-not-using-indexesYesYes  GlobalYes
- Variable: log_queries_not_using_indexes  Yes GlobalYes
log-rawYesYes    
log-short-formatYesYes    
log-slave-updatesYesYes  GlobalNo
- Variable: log_slave_updates  Yes GlobalNo
log_slave_updatesYesYesYes GlobalNo
log_slow_admin_statements  Yes GlobalYes
log-slow-admin-statementsYesYes    
log-slow-queriesYesYes  GlobalYes
- Variable: log_slow_queries  Yes GlobalYes
log_slow_slave_statements  Yes GlobalYes
log-slow-slave-statementsYesYes    
log-tcYesYes    
log-tc-sizeYesYes    
log_throttle_queries_not_using_indexes  Yes GlobalYes
log-warningsYesYes  VariesYes
- Variable: log_warnings  Yes VariesYes
long_query_timeYesYesYes BothYes
low-priority-updatesYesYes  BothYes
- Variable: low_priority_updates  Yes BothYes
lower_case_file_system  Yes GlobalNo
lower_case_table_namesYesYesYes GlobalNo
master-info-fileYesYes    
master_info_repositoryYesYesYes GlobalYes
master-info-repositoryYesYes    
- Variable: master_info_repository      
master-retry-countYesYes    
master_verify_checksum  Yes GlobalYes
master-verify-checksumYesYes    
- Variable: master_verify_checksum      
max_allowed_packetYesYesYes GlobalYes
max_binlog_cache_sizeYesYesYes GlobalYes
max-binlog-dump-eventsYesYes    
max_binlog_sizeYesYesYes GlobalYes
max_binlog_stmt_cache_sizeYesYesYes GlobalYes
max_connect_errorsYesYesYes GlobalYes
max_connectionsYesYesYes GlobalYes
max_delayed_threadsYesYesYes BothYes
max_error_countYesYesYes BothYes
max_heap_table_sizeYesYesYes BothYes
max_insert_delayed_threads  Yes BothYes
max_join_sizeYesYesYes BothYes
max_length_for_sort_dataYesYesYes BothYes
max_prepared_stmt_countYesYesYes GlobalYes
max_relay_log_sizeYesYesYes GlobalYes
max_seeks_for_keyYesYesYes BothYes
max_sort_lengthYesYesYes BothYes
max_sp_recursion_depthYesYesYes BothYes
Max_used_connections   YesGlobalNo
max_user_connectionsYesYesYes BothYes
max_write_lock_countYesYesYes GlobalYes
memlockYesYes    
- Variable: locked_in_memory      
metadata_locks_cache_size  Yes GlobalNo
metadata_locks_hash_instances  Yes GlobalNo
min-examined-row-limitYesYesYes BothYes
myisam-block-sizeYesYes    
myisam_data_pointer_sizeYesYesYes GlobalYes
myisam_max_sort_file_sizeYesYesYes GlobalYes
myisam_mmap_sizeYesYesYes GlobalNo
myisam-recover-optionsYesYes    
- Variable: myisam_recover_options      
myisam_recover_options  Yes GlobalNo
myisam_repair_threadsYesYesYes BothYes
myisam_sort_buffer_sizeYesYesYes BothYes
myisam_stats_methodYesYesYes BothYes
myisam_use_mmapYesYesYes GlobalYes
named_pipe  Yes GlobalNo
Ndb_api_bytes_received_count   YesGlobalNo
Ndb_api_bytes_received_count_session   YesSessionNo
Ndb_api_bytes_received_count_slave   YesGlobalNo
Ndb_api_bytes_sent_count   YesGlobalNo
Ndb_api_bytes_sent_count_session   YesSessionNo
Ndb_api_bytes_sent_count_slave   YesGlobalNo
Ndb_api_event_bytes_count   YesGlobalNo
Ndb_api_event_bytes_count_injector   YesGlobalNo
Ndb_api_event_data_count   YesGlobalNo
Ndb_api_event_data_count_injector   YesGlobalNo
Ndb_api_event_nondata_count   YesGlobalNo
Ndb_api_event_nondata_count_injector   YesGlobalNo
Ndb_api_pk_op_count   YesGlobalNo
Ndb_api_pk_op_count_session   YesSessionNo
Ndb_api_pk_op_count_slave   YesGlobalNo
Ndb_api_pruned_scan_count   YesGlobalNo
Ndb_api_pruned_scan_count_session   YesSessionNo
Ndb_api_pruned_scan_count_slave   YesGlobalNo
Ndb_api_range_scan_count   YesGlobalNo
Ndb_api_range_scan_count_session   YesSessionNo
Ndb_api_range_scan_count_slave   YesGlobalNo
Ndb_api_read_row_count   YesGlobalNo
Ndb_api_read_row_count_session   YesSessionNo
Ndb_api_read_row_count_slave   YesGlobalNo
Ndb_api_scan_batch_count   YesGlobalNo
Ndb_api_scan_batch_count_session   YesSessionNo
Ndb_api_scan_batch_count_slave   YesGlobalNo
Ndb_api_table_scan_count   YesGlobalNo
Ndb_api_table_scan_count_session   YesSessionNo
Ndb_api_table_scan_count_slave   YesGlobalNo
Ndb_api_trans_abort_count   YesGlobalNo
Ndb_api_trans_abort_count_session   YesSessionNo
Ndb_api_trans_abort_count_slave   YesGlobalNo
Ndb_api_trans_close_count   YesGlobalNo
Ndb_api_trans_close_count_session   YesSessionNo
Ndb_api_trans_close_count_slave   YesGlobalNo
Ndb_api_trans_commit_count   YesGlobalNo
Ndb_api_trans_commit_count_session   YesSessionNo
Ndb_api_trans_commit_count_slave   YesGlobalNo
Ndb_api_trans_local_read_row_count   YesGlobalNo
Ndb_api_trans_local_read_row_count_session   YesSessionNo
Ndb_api_trans_local_read_row_count_slave   YesGlobalNo
Ndb_api_trans_start_count   YesGlobalNo
Ndb_api_trans_start_count_session   YesSessionNo
Ndb_api_trans_start_count_slave   YesGlobalNo
Ndb_api_uk_op_count   YesGlobalNo
Ndb_api_uk_op_count_session   YesSessionNo
Ndb_api_uk_op_count_slave   YesGlobalNo
Ndb_api_wait_exec_complete_count   YesGlobalNo
Ndb_api_wait_exec_complete_count_session   YesSessionNo
Ndb_api_wait_exec_complete_count_slave   YesGlobalNo
Ndb_api_wait_meta_request_count   YesGlobalNo
Ndb_api_wait_meta_request_count_session   YesSessionNo
Ndb_api_wait_meta_request_count_slave   YesGlobalNo
Ndb_api_wait_nanos_count   YesGlobalNo
Ndb_api_wait_nanos_count_session   YesSessionNo
Ndb_api_wait_nanos_count_slave   YesGlobalNo
Ndb_api_wait_scan_result_count   YesGlobalNo
Ndb_api_wait_scan_result_count_session   YesSessionNo
Ndb_api_wait_scan_result_count_slave   YesGlobalNo
ndb_autoincrement_prefetch_szYesYesYes BothYes
ndb-batch-sizeYesYesYes GlobalNo
ndb-blob-read-batch-bytesYesYesYes BothYes
ndb-blob-write-batch-bytesYesYesYes BothYes
ndb_cache_check_timeYesYesYes GlobalYes
ndb-cluster-connection-poolYesYesYes GlobalNo
Ndb_cluster_node_id   YesBothNo
Ndb_config_from_host   YesBothNo
Ndb_config_from_port   YesBothNo
Ndb_conflict_fn_epoch   YesGlobalNo
Ndb_conflict_fn_epoch_trans   YesGlobalNo
Ndb_conflict_fn_max   YesGlobalNo
Ndb_conflict_fn_old   YesGlobalNo
Ndb_conflict_trans_conflict_commit_count   YesGlobalNo
Ndb_conflict_trans_detect_iter_count   YesGlobalNo
Ndb_conflict_trans_reject_count   YesGlobalNo
Ndb_conflict_trans_row_conflict_count   YesGlobalNo
Ndb_conflict_trans_row_reject_count   YesGlobalNo
ndb-connectstringYesYes    
ndb-deferred-constraintsYesYes  BothYes
- Variable: ndb_deferred_constraints  Yes BothYes
ndb_deferred_constraintsYesYesYes BothYes
ndb_distributionYesYesYes GlobalYes
ndb-distributionYesYes  GlobalYes
- Variable: ndb_distribution  Yes GlobalYes
ndb_eventbuffer_free_percentYesYesYes GlobalYes
ndb_eventbuffer_max_allocYesYesYes GlobalYes
Ndb_execute_count   YesGlobalNo
ndb_extra_loggingYesYesYes GlobalYes
ndb_force_sendYesYesYes BothYes
ndb_index_stat_cache_entriesYesYesYes BothYes
ndb_index_stat_enableYesYesYes BothYes
ndb_index_stat_optionYesYesYes BothYes
ndb_index_stat_update_freqYesYesYes BothYes
ndb_join_pushdown  Yes BothYes
Ndb_last_commit_epoch_server   YesGlobalNo
Ndb_last_commit_epoch_session   YesSessionNo
ndb-log-apply-statusYesYes  GlobalNo
- Variable: ndb_log_apply_status  Yes GlobalNo
ndb_log_apply_statusYesYesYes GlobalNo
ndb_log_binYes Yes BothYes
ndb_log_binlog_indexYes Yes GlobalYes
ndb_log_empty_epochsYesYesYes GlobalYes
ndb-log-empty-epochsYesYesYes GlobalYes
ndb-log-exclusive-readsYesYes  BothYes
- Variable: ndb_log_exclusive_reads  Yes BothYes
ndb_log_exclusive_readsYesYesYes BothYes
ndb-log-origYesYes  GlobalNo
- Variable: ndb_log_orig  Yes GlobalNo
ndb_log_origYesYesYes GlobalNo
ndb-log-transaction-idYesYes  GlobalNo
- Variable: ndb_log_transaction_id  Yes GlobalNo
ndb_log_transaction_id  Yes GlobalNo
ndb-log-update-as-writeYesYesYes GlobalYes
ndb_log_updated_onlyYesYesYes GlobalYes
ndb-mgmd-hostYesYes    
ndb-nodeidYesYes YesGlobalNo
Ndb_number_of_data_nodes   YesGlobalNo
ndb_optimization_delay  Yes GlobalYes
ndb_optimized_node_selectionYesYesYes GlobalNo
Ndb_pruned_scan_count   YesGlobalNo
Ndb_pushed_queries_defined   YesGlobalNo
Ndb_pushed_queries_dropped   YesGlobalNo
Ndb_pushed_queries_executed   YesGlobalNo
Ndb_pushed_reads   YesGlobalNo
ndb-recv-thread-activation-thresholdYesYes    
- Variable: ndb_recv_thread_activation_threshold      
ndb_recv_thread_activation_threshold      
ndb-recv-thread-cpu-maskYesYes    
- Variable: ndb_recv_thread_cpu_mask      
ndb_recv_thread_cpu_mask  Yes GlobalYes
ndb_report_thresh_binlog_epoch_slipYesYes    
ndb_report_thresh_binlog_mem_usageYesYes    
Ndb_scan_count   YesGlobalNo
ndb_show_foreign_key_mock_tablesYesYesYes GlobalYes
ndb_slave_conflict_roleYesYesYes GlobalYes
Ndb_slave_last_conflict_epoch  Yes GlobalNo
Ndb_slave_max_replicated_epoch  Yes GlobalNo
ndb_table_no_logging  Yes SessionYes
ndb_table_temporary  Yes SessionYes
ndb-transid-mysql-connection-mapYes     
ndb_use_copying_alter_table  Yes BothNo
ndb_use_exact_count  Yes BothYes
ndb_use_transactionsYesYesYes BothYes
ndb_version  Yes GlobalNo
ndb_version_string  Yes GlobalNo
ndb-wait-connectedYesYesYes GlobalNo
ndb-wait-setupYesYesYes GlobalNo
ndbclusterYesYes    
- Variable: have_ndbcluster      
ndbinfo_database  Yes GlobalNo
ndbinfo_max_bytesYes Yes BothYes
ndbinfo_max_rowsYes Yes BothYes
ndbinfo_offline  Yes GlobalYes
ndbinfo_show_hiddenYes Yes BothYes
ndbinfo_table_prefixYes Yes BothYes
ndbinfo_version  Yes GlobalNo
net_buffer_lengthYesYesYes BothYes
net_read_timeoutYesYesYes BothYes
net_retry_countYesYesYes BothYes
net_write_timeoutYesYesYes BothYes
newYesYesYes BothYes
no-defaultsYes     
Not_flushed_delayed_rows   YesGlobalNo
oldYesYesYes GlobalNo
old-alter-tableYesYes  BothYes
- Variable: old_alter_table  Yes BothYes
old_passwords  Yes BothYes
old-style-user-limitsYesYes    
one-threadYesYes    
Open_files   YesGlobalNo
open-files-limitYesYes  GlobalNo
- Variable: open_files_limit  Yes GlobalNo
Open_streams   YesGlobalNo
Open_table_definitions   YesGlobalNo
Open_tables   YesBothNo
Opened_files   YesGlobalNo
Opened_table_definitions   YesBothNo
Opened_tables   YesBothNo
optimizer_join_cache_levelYesYesYes BothYes
optimizer_prune_levelYesYesYes BothYes
optimizer_search_depthYesYesYes BothYes
optimizer_switchYesYesYes BothYes
optimizer_trace  Yes BothYes
optimizer_trace_features  Yes BothYes
optimizer_trace_limit  Yes BothYes
optimizer_trace_max_mem_size  Yes BothYes
optimizer_trace_offset  Yes BothYes
partitionYesYes    
- Variable: have_partitioning      
performance_schemaYesYesYes GlobalNo
Performance_schema_accounts_lost   YesGlobalNo
performance_schema_accounts_sizeYesYesYes GlobalNo
Performance_schema_cond_classes_lost   YesGlobalNo
Performance_schema_cond_instances_lost   YesGlobalNo
performance-schema-consumer-events-stages-currentYesYes    
performance-schema-consumer-events-stages-historyYesYes    
performance-schema-consumer-events-stages-history-longYesYes    
performance-schema-consumer-events-statements-currentYesYes    
performance-schema-consumer-events-statements-historyYesYes    
performance-schema-consumer-events-statements-history-longYesYes    
performance-schema-consumer-events-waits-currentYesYes    
performance-schema-consumer-events-waits-historyYesYes    
performance-schema-consumer-events-waits-history-longYesYes    
performance-schema-consumer-global-instrumentationYesYes    
performance-schema-consumer-statements-digestYesYes    
performance-schema-consumer-thread-instrumentationYesYes    
Performance_schema_digest_lost   YesGlobalNo
performance_schema_digests_sizeYesYesYes GlobalNo
performance_schema_events_stages_history_long_sizeYesYesYes GlobalNo
performance_schema_events_stages_history_sizeYesYesYes GlobalNo
performance_schema_events_statements_history_long_sizeYesYesYes GlobalNo
performance_schema_events_statements_history_sizeYesYesYes GlobalNo
performance_schema_events_waits_history_long_sizeYesYesYes GlobalNo
performance_schema_events_waits_history_sizeYesYesYes GlobalNo
Performance_schema_file_classes_lost   YesGlobalNo
Performance_schema_file_handles_lost   YesGlobalNo
Performance_schema_file_instances_lost   YesGlobalNo
Performance_schema_hosts_lost   YesGlobalNo
performance_schema_hosts_sizeYesYesYes GlobalNo
performance-schema-instrumentYesYes    
Performance_schema_locker_lost   YesGlobalNo
performance_schema_max_cond_classesYesYesYes GlobalNo
performance_schema_max_cond_instancesYesYesYes GlobalNo
performance_schema_max_file_classesYesYesYes GlobalNo
performance_schema_max_file_handlesYesYesYes GlobalNo
performance_schema_max_file_instancesYesYesYes GlobalNo
performance_schema_max_mutex_classesYesYesYes GlobalNo
performance_schema_max_mutex_instancesYesYesYes GlobalNo
performance_schema_max_rwlock_classesYesYesYes GlobalNo
performance_schema_max_rwlock_instancesYesYesYes GlobalNo
performance_schema_max_socket_classesYesYesYes GlobalNo
performance_schema_max_socket_instancesYesYesYes GlobalNo
performance_schema_max_stage_classesYesYesYes GlobalNo
performance_schema_max_statement_classesYesYesYes GlobalNo
performance_schema_max_table_handlesYesYesYes GlobalNo
performance_schema_max_table_instancesYesYesYes GlobalNo
performance_schema_max_thread_classesYesYesYes GlobalNo
performance_schema_max_thread_instancesYesYesYes GlobalNo
Performance_schema_mutex_classes_lost   YesGlobalNo
Performance_schema_mutex_instances_lost   YesGlobalNo
Performance_schema_rwlock_classes_lost   YesGlobalNo
Performance_schema_rwlock_instances_lost   YesGlobalNo
Performance_schema_session_connect_attrs_lost   YesGlobalNo
performance_schema_session_connect_attrs_sizeYesYesYes GlobalNo
performance_schema_setup_actors_sizeYesYesYes GlobalNo
performance_schema_setup_objects_sizeYesYesYes GlobalNo
Performance_schema_socket_classes_lost   YesGlobalNo
Performance_schema_socket_instances_lost   YesGlobalNo
Performance_schema_stage_classes_lost   YesGlobalNo
Performance_schema_statement_classes_lost   YesGlobalNo
Performance_schema_table_handles_lost   YesGlobalNo
Performance_schema_table_instances_lost   YesGlobalNo
Performance_schema_thread_classes_lost   YesGlobalNo
Performance_schema_thread_instances_lost   YesGlobalNo
Performance_schema_users_lost   YesGlobalNo
performance_schema_users_sizeYesYesYes GlobalNo
pid-fileYesYes  GlobalNo
- Variable: pid_file  Yes GlobalNo
pluginYesYes    
plugin_dirYesYesYes GlobalNo
plugin-loadYesYes    
plugin-load-addYesYes    
portYesYesYes GlobalNo
port-open-timeoutYesYes    
preload_buffer_sizeYesYesYes BothYes
Prepared_stmt_count   YesGlobalNo
print-defaultsYes     
profiling  Yes BothYes
profiling_history_sizeYesYesYes BothYes
protocol_version  Yes GlobalNo
proxy_user  Yes SessionNo
pseudo_slave_mode  Yes SessionYes
pseudo_thread_id  Yes SessionYes
Qcache_free_blocks   YesGlobalNo
Qcache_free_memory   YesGlobalNo
Qcache_hits   YesGlobalNo
Qcache_inserts   YesGlobalNo
Qcache_lowmem_prunes   YesGlobalNo
Qcache_not_cached   YesGlobalNo
Qcache_queries_in_cache   YesGlobalNo
Qcache_total_blocks   YesGlobalNo
Queries   YesBothNo
query_alloc_block_sizeYesYesYes BothYes
query_cache_limitYesYesYes GlobalYes
query_cache_min_res_unitYesYesYes GlobalYes
query_cache_sizeYesYesYes GlobalYes
query_cache_typeYesYesYes BothYes
query_cache_wlock_invalidateYesYesYes BothYes
query_prealloc_sizeYesYesYes BothYes
Questions   YesBothNo
rand_seed1  Yes SessionYes
rand_seed2  Yes SessionYes
range_alloc_block_sizeYesYesYes BothYes
read_buffer_sizeYesYesYes BothYes
read_onlyYesYesYes GlobalYes
read_rnd_buffer_sizeYesYesYes BothYes
relay-logYesYes  GlobalNo
- Variable: relay_log  Yes GlobalNo
relay_log_basename  Yes GlobalNo
relay-log-indexYesYes  GlobalNo
- Variable: relay_log_index  Yes GlobalNo
relay_log_indexYesYesYes GlobalNo
relay-log-info-fileYesYes    
- Variable: relay_log_info_file      
relay_log_info_fileYesYesYes GlobalNo
relay-log-info-repositoryYesYes    
- Variable: relay_log_info_repository      
relay_log_info_repository  Yes GlobalYes
relay_log_purgeYesYesYes GlobalYes
relay_log_recoveryYesYesYes GlobalVaries
relay-log-recoveryYesYes    
- Variable: relay_log_recovery      
relay_log_space_limitYesYesYes GlobalNo
removeYes     
replicate-do-dbYesYes    
replicate-do-tableYesYes    
replicate-ignore-dbYesYes    
replicate-ignore-tableYesYes    
replicate-rewrite-dbYesYes    
replicate-same-server-idYesYes    
replicate-wild-do-tableYesYes    
replicate-wild-ignore-tableYesYes    
report-hostYesYes  GlobalNo
- Variable: report_host  Yes GlobalNo
report-passwordYesYes  GlobalNo
- Variable: report_password  Yes GlobalNo
report-portYesYes  GlobalNo
- Variable: report_port  Yes GlobalNo
report-userYesYes  GlobalNo
- Variable: report_user  Yes GlobalNo
Rpl_semi_sync_master_clients   YesGlobalNo
rpl_semi_sync_master_enabled  Yes GlobalYes
Rpl_semi_sync_master_net_avg_wait_time   YesGlobalNo
Rpl_semi_sync_master_net_wait_time   YesGlobalNo
Rpl_semi_sync_master_net_waits   YesGlobalNo
Rpl_semi_sync_master_no_times   YesGlobalNo
Rpl_semi_sync_master_no_tx   YesGlobalNo
Rpl_semi_sync_master_status   YesGlobalNo
Rpl_semi_sync_master_timefunc_failures   YesGlobalNo
rpl_semi_sync_master_timeout  Yes GlobalYes
rpl_semi_sync_master_trace_level  Yes GlobalYes
Rpl_semi_sync_master_tx_avg_wait_time   YesGlobalNo
Rpl_semi_sync_master_tx_wait_time   YesGlobalNo
Rpl_semi_sync_master_tx_waits   YesGlobalNo
rpl_semi_sync_master_wait_no_slave  Yes GlobalYes
Rpl_semi_sync_master_wait_pos_backtraverse   YesGlobalNo
Rpl_semi_sync_master_wait_sessions   YesGlobalNo
Rpl_semi_sync_master_yes_tx   YesGlobalNo
rpl_semi_sync_slave_enabled  Yes GlobalYes
Rpl_semi_sync_slave_status   YesGlobalNo
rpl_semi_sync_slave_trace_level  Yes GlobalYes
rpl_stop_slave_timeoutYesYesYes GlobalYes
Rsa_public_key   YesGlobalNo
safe-modeYesYes    
safe-user-createYesYes    
secure-authYesYes  GlobalYes
- Variable: secure_auth  Yes GlobalYes
secure-file-privYesYes  GlobalNo
- Variable: secure_file_priv  Yes GlobalNo
Select_full_join   YesBothNo
Select_full_range_join   YesBothNo
Select_range   YesBothNo
Select_range_check   YesBothNo
Select_scan   YesBothNo
server-idYesYes  GlobalYes
- Variable: server_id  Yes GlobalYes
server_id_bitsYesYesYes GlobalNo
server-id-bitsYesYes  GlobalNo
- Variable: server_id_bits  Yes GlobalNo
server_uuid  Yes GlobalNo
sha256_password_private_key_path  Yes GlobalNo
sha256_password_public_key_path  Yes GlobalNo
shared_memoryYesYesYes GlobalNo
shared_memory_base_name  Yes GlobalNo
show-slave-auth-infoYesYes    
simplified_binlog_gtid_recoveryYesYesYes GlobalNo
skip-character-set-client-handshakeYesYes    
skip-concurrent-insertYesYes    
- Variable: concurrent_insert      
skip-event-schedulerYesYes    
skip_external_lockingYesYesYes GlobalNo
skip-grant-tablesYesYes    
skip-host-cacheYesYes    
skip-name-resolveYesYes  GlobalNo
- Variable: skip_name_resolve  Yes GlobalNo
skip-ndbclusterYesYes    
skip-networkingYesYes  GlobalNo
- Variable: skip_networking  Yes GlobalNo
skip-newYesYes    
skip-partitionYesYes    
skip-show-databaseYesYes  GlobalNo
- Variable: skip_show_database  Yes GlobalNo
skip-slave-startYesYes    
skip-sslYesYes    
skip-stack-traceYesYes    
skip-symbolic-linksYes     
skip-thread-priorityYesYes    
slave_allow_batchingYesYesYes GlobalYes
slave_checkpoint_groupYesYesYes GlobalYes
slave-checkpoint-groupYesYes    
- Variable: slave_checkpoint_group      
slave_checkpoint_periodYesYesYes GlobalYes
slave-checkpoint-periodYesYes    
- Variable: slave_checkpoint_period      
slave_compressed_protocolYesYesYes GlobalYes
slave_exec_modeYesYesYes GlobalYes
Slave_heartbeat_period   YesGlobalNo
Slave_last_heartbeat   YesGlobalNo
slave-load-tmpdirYesYes  GlobalNo
- Variable: slave_load_tmpdir  Yes GlobalNo
slave_max_allowed_packet  Yes GlobalYes
slave-max-allowed-packetYesYes    
- Variable: slave_max_allowed_packet      
slave-net-timeoutYesYes  GlobalYes
- Variable: slave_net_timeout  Yes GlobalYes
Slave_open_temp_tables   YesGlobalNo
slave_parallel_workersYes Yes GlobalYes
slave-parallel-workersYesYes    
- Variable: slave_parallel_workers      
slave_pending_jobs_size_max  Yes GlobalYes
slave-pending-jobs-size-maxYes     
- Variable: slave_pending_jobs_size_max      
Slave_received_heartbeats   YesGlobalNo
Slave_retried_transactions   YesGlobalNo
slave-rows-search-algorithmsYesYes    
- Variable: slave_rows_search_algorithms      
slave_rows_search_algorithms  Yes GlobalYes
Slave_running   YesGlobalNo
slave-skip-errorsYesYes  GlobalNo
- Variable: slave_skip_errors  Yes GlobalNo
slave_sql_verify_checksum  Yes GlobalYes
slave-sql-verify-checksumYesYes    
slave_transaction_retriesYesYesYes GlobalYes
slave_type_conversionsYesYesYes GlobalNo
Slow_launch_threads   YesBothNo
slow_launch_timeYesYesYes GlobalYes
Slow_queries   YesBothNo
slow-query-logYesYes  GlobalYes
- Variable: slow_query_log  Yes GlobalYes
slow_query_log_fileYesYesYes GlobalYes
slow-start-timeoutYesYes    
socketYesYesYes GlobalNo
sort_buffer_sizeYesYesYes BothYes
Sort_merge_passes   YesBothNo
Sort_range   YesBothNo
Sort_rows   YesBothNo
Sort_scan   YesBothNo
sporadic-binlog-dump-failYesYes    
sql_auto_is_null  Yes BothYes
sql_big_selects  Yes BothYes
sql_big_tables  Yes BothYes
sql_buffer_result  Yes BothYes
sql_log_bin  Yes BothYes
sql_log_off  Yes BothYes
sql_low_priority_updates  Yes BothYes
sql_max_join_size  Yes BothYes
sql-modeYesYes  BothYes
- Variable: sql_mode  Yes BothYes
sql_notes  Yes BothYes
sql_quote_show_create  Yes BothYes
sql_safe_updates  Yes BothYes
sql_select_limit  Yes BothYes
sql_slave_skip_counter  Yes GlobalYes
sql_warnings  Yes BothYes
sslYesYes    
Ssl_accept_renegotiates   YesGlobalNo
Ssl_accepts   YesGlobalNo
ssl-caYesYes  GlobalNo
- Variable: ssl_ca  Yes GlobalNo
Ssl_callback_cache_hits   YesGlobalNo
ssl-capathYesYes  GlobalNo
- Variable: ssl_capath  Yes GlobalNo
ssl-certYesYes  GlobalNo
- Variable: ssl_cert  Yes GlobalNo
ssl-cipherYesYes  GlobalNo
- Variable: ssl_cipher  Yes GlobalNo
Ssl_cipher   YesBothNo
Ssl_cipher_list   YesBothNo
Ssl_client_connects   YesGlobalNo
Ssl_connect_renegotiates   YesGlobalNo
ssl-crlYesYes  GlobalNo
- Variable: ssl_crl  Yes GlobalNo
ssl-crlpathYesYes  GlobalNo
- Variable: ssl_crlpath  Yes GlobalNo
Ssl_ctx_verify_depth   YesGlobalNo
Ssl_ctx_verify_mode   YesGlobalNo
Ssl_default_timeout   YesBothNo
Ssl_finished_accepts   YesGlobalNo
Ssl_finished_connects   YesGlobalNo
ssl-keyYesYes  GlobalNo
- Variable: ssl_key  Yes GlobalNo
Ssl_server_not_after   YesBothNo
Ssl_server_not_before   YesBothNo
Ssl_session_cache_hits   YesGlobalNo
Ssl_session_cache_misses   YesGlobalNo
Ssl_session_cache_mode   YesGlobalNo
Ssl_session_cache_overflows   YesGlobalNo
Ssl_session_cache_size   YesGlobalNo
Ssl_session_cache_timeouts   YesGlobalNo
Ssl_sessions_reused   YesBothNo
Ssl_used_session_cache_entries   YesGlobalNo
Ssl_verify_depth   YesBothNo
Ssl_verify_mode   YesBothNo
Ssl_version   YesBothNo
standaloneYesYes    
storage_engine  Yes BothYes
stored_program_cacheYesYesYes GlobalYes
super-large-pagesYesYes    
symbolic-linksYesYes    
sync_binlogYesYesYes GlobalYes
sync_frmYesYesYes GlobalYes
sync_master_infoYesYesYes GlobalYes
sync_relay_logYesYesYes GlobalYes
sync_relay_log_infoYesYesYes GlobalYes
sysdate-is-nowYesYes    
system_time_zone  Yes GlobalNo
table_definition_cache  Yes GlobalYes
Table_locks_immediate   YesGlobalNo
Table_locks_waited   YesGlobalNo
table_open_cache  Yes GlobalYes
Table_open_cache_hits   YesBothNo
table_open_cache_instances  Yes GlobalNo
Table_open_cache_misses   YesBothNo
Table_open_cache_overflows   YesBothNo
tc-heuristic-recoverYesYes    
Tc_log_max_pages_used   YesGlobalNo
Tc_log_page_size   YesGlobalNo
Tc_log_page_waits   YesGlobalNo
temp-poolYesYes    
thread_cache_sizeYesYesYes GlobalYes
thread_concurrencyYesYesYes GlobalNo
thread_handlingYesYesYes GlobalNo
thread_pool_algorithmYesYesYes GlobalNo
thread_pool_high_priority_connectionYesYesYes BothYes
thread_pool_max_unused_threadsYesYesYes GlobalYes
thread_pool_prio_kickup_timerYesYesYes BothYes
thread_pool_sizeYesYesYes GlobalNo
thread_pool_stall_limitYesYesYes GlobalYes
thread_stackYesYesYes GlobalNo
Threads_cached   YesGlobalNo
Threads_connected   YesGlobalNo
Threads_created   YesGlobalNo
Threads_running   YesGlobalNo
time_format  Yes GlobalNo
time_zone  Yes BothYes
timed_mutexesYesYesYes GlobalYes
timestamp  Yes SessionYes
tmp_table_sizeYesYesYes BothYes
tmpdirYesYesYes GlobalNo
transaction_alloc_block_sizeYesYesYes BothYes
transaction_allow_batching  Yes SessionYes
transaction-isolationYesYes    
- Variable: tx_isolation      
transaction_prealloc_sizeYesYesYes BothYes
transaction-read-onlyYesYes    
- Variable: tx_read_only      
tx_isolation  Yes BothYes
tx_read_only  Yes BothYes
unique_checks  Yes BothYes
updatable_views_with_limitYesYesYes BothYes
Uptime   YesGlobalNo
Uptime_since_flush_status   YesGlobalNo
userYesYes    
validate-passwordYesYes    
validate_password_dictionary_file  Yes GlobalNo
validate_password_length  Yes GlobalYes
validate_password_mixed_case_count  Yes GlobalYes
validate_password_number_count  Yes GlobalYes
validate_password_policy  Yes GlobalYes
validate_password_special_char_count  Yes GlobalYes
validate_user_plugins  Yes GlobalNo
verboseYesYes    
version  Yes GlobalNo
version_comment  Yes GlobalNo
version_compile_machine  Yes GlobalNo
version_compile_os  Yes GlobalNo
wait_timeoutYesYesYes BothYes
warning_count  Yes SessionNo

[a] This option is dynamic, but only the server should set this information. You should not set the value of this variable manually.

[b] This option is dynamic, but only the server should set this information. You should not set the value of this variable manually.


5.1.2 Server Configuration Defaults

The MySQL server has many operating parameters, which you can change at server startup using command-line options or configuration files (option files). It is also possible to change many parameters at runtime. For general instructions on setting parameters at startup or runtime, see Section 5.1.3, “Server Command Options”, and Section 5.1.4, “Server System Variables”.

5.1.2.1 Changes to Server Defaults

Beginning with MySQL 5.6.6, several MySQL Server parameter defaults differ from the defaults in previous releases. The motivation for these changes is to provide better out-of-box performance and to reduce the need for database administrators to change settings manually.

In some cases, a parameter has a different fixed default value. In other cases, the server autosizes a parameter at startup using a formula based on other related parameters or server host configuration, rather than using a fixed value. For example, the setting for back_log is its previous default of 50, adjusted up by an amount proportional to the value of max_connections. The idea behind autosizing is that when the server has information available to make a decision about a parameter setting likely to be better than a fixed default, it will.

The following table summarizes changes to defaults. The Version column indicates when each default changed. For variables that are autosized, the main variable description provides additional detail about the sizing algorithm. See Section 5.1.4, “Server System Variables”, and Section 14.12, “InnoDB Startup Options and System Variables”. Any of these default settings can be overridden by specifying an explicit value at server startup.

Table 5.2 Changes to Server Defaults in MySQL 5.6

ParameterOld DefaultNew DefaultVersion
back_log50Autosized using max_connections5.6.6
binlog_checksumNONECRC325.6.6
--binlog-row-event-max-size102481925.6.6
flush_time1800 (on Windows)05.6.6
host_cache_size128Autosized using max_connections5.6.8
innodb_autoextend_increment8645.6.6
innodb_buffer_pool_instances18 (platform dependent)5.6.6
innodb_concurrency_tickets50050005.6.6
innodb_data_file_pathibdata1:10M:autoextendibdata1:12M:autoextend5.6.7
innodb_file_per_table015.6.6
innodb_log_file_size5MB48MB5.6.8
innodb_old_blocks_time010005.6.6
innodb_open_files300Autosized using innodb_file_per_table, table_open_cache5.6.6
innodb_stats_on_metadataONOFF5.6.6
join_buffer_size128KB256KB5.6.6
max_allowed_packet1MB4MB5.6.6
max_connect_errors101005.6.6
open_files_limit0Autosized using max_connections5.6.8
performance_schemaOFFON5.6.6
performance_schema_events_waits_history_long_size10000Autosized5.6.6
performance_schema_events_waits_history_size10Autosized5.6.6
performance_schema_max_cond_instances1000Autosized5.6.6
performance_schema_max_file_instances10000Autosized5.6.6
performance_schema_max_mutex_instances1000000Autosized5.6.6
performance_schema_max_rwlock_instances1000000Autosized5.6.6
performance_schema_max_table_handles100000Autosized5.6.6
performance_schema_max_table_instances50000Autosized5.6.6
performance_schema_max_thread_instances1000Autosized5.6.6
query_cache_size01M5.6.8
query_cache_typeONOFF5.6.8
secure_authOFFON5.6.7
sql_mode'' (empty string)NO_ENGINE_SUBSTITUTION5.6.6
sync_master_info0100005.6.6
sync_relay_log0100005.6.6
sync_relay_log_info0100005.6.6
table_definition_cache400Autosized using table_open_cache5.6.8
table_open_cache40020005.6.8
thread_cache_size0Autosized using max_connections5.6.8

In MySQL 5.6.6, the default for innodb_checksum_algorithm was changed from INNODB to CRC32. For compatibility reasons, the default was returned in 5.6.7 to INNODB.

5.1.2.2 Using a Sample Default Server Configuration File

As of MySQL 5.6.8, on Unix platforms, mysql_install_db creates a default option file named my.cnf in the base installation directory. This file is created from a template included in the distribution package named my-default.cnf. You can find the template in or under the base installation directory. When started using mysqld_safe, the server uses my.cnf file by default. If my.cnf already exists, mysql_install_db assumes it to be in use and writes a new file named my-new.cnf instead.

With one exception, the settings in the default option file are commented and have no effect. The exception is that the file changes the sql_mode system variable from its default of NO_ENGINE_SUBSTITUTION to also include STRICT_TRANS_TABLES:

sql_mode=NO_ENGINE_SUBSTITUTION,STRICT_TRANS_TABLES

This setting produces a server configuration that results in errors rather than warnings for bad data in operations that modify transactional tables. See Section 5.1.7, “Server SQL Modes”.

The my-default.cnf template replaces the older sample option files formerly supplied with MySQL distributions (my-small.cnf, my-medium.cnf, my-large.cnf, and my-huge.cnf). As of MySQL 5.6.8, these older files are no longer distributed.

On Windows, MySQL Installer interacts with the user and creates a file named my.ini in the base installation directory as the default option file. If you install on Windows from a Zip archive, you can copy the my-default.ini template file in the base installation directory to my.ini and use the latter as the default option file.

Note

On Windows, the .ini or .cnf option file extension might not be displayed.

On any platform, after completing the installation process, you can edit the default option file at any time to modify the parameters used by the server. For example, to use a parameter setting in the file that is commented with a # character at the beginning of the line, remove the #, and modify the parameter value if necessary. To disable a To disable a setting, either add a # to the beginning of the line or remove it.

For additional information about option file format and syntax, see Section 4.2.6, “Using Option Files”.

Before MySQL 5.6.8, MySQL distributions include several sample option files that can be used as a basis for tuning the MySQL server. Look for files named my-small.cnf, my-medium.cnf, my-large.cnf, and my-huge.cnf, which are sample files for small, medium, large, and very large systems. On Windows, the extension is .ini rather than .cnf.

For a binary distribution, look for the sample files in or under your installation directory. If you have a source distribution, look in the support-files directory. To use a sample file as a base configuration file, rename a copy of it and place the copy in the appropriate location. Regarding names and appropriate location, see the general information provided in Section 4.2.6, “Using Option Files”.

5.1.3 Server Command Options

When you start the mysqld server, you can specify program options using any of the methods described in Section 4.2.3, “Specifying Program Options”. The most common methods are to provide options in an option file or on the command line. However, in most cases it is desirable to make sure that the server uses the same options each time it runs. The best way to ensure this is to list them in an option file. See Section 4.2.6, “Using Option Files”. That section also describes option file format and syntax.

mysqld reads options from the [mysqld] and [server] groups. mysqld_safe reads options from the [mysqld], [server], [mysqld_safe], and [safe_mysqld] groups. mysql.server reads options from the [mysqld] and [mysql.server] groups.

An embedded MySQL server usually reads options from the [server], [embedded], and [xxxxx_SERVER] groups, where xxxxx is the name of the application into which the server is embedded.

mysqld accepts many command options. For a brief summary, execute mysqld --help. To see the full list, use mysqld --verbose --help.

The following list shows some of the most common server options. Additional options are described in other sections:

You can also set the values of server system variables by using variable names as options, as described at the end of this section.

Some options control the size of buffers or caches. For a given buffer, the server might need to allocate internal data structures. These structures typically are allocated from the total memory allocated to the buffer, and the amount of space required might be platform dependent. This means that when you assign a value to an option that controls a buffer size, the amount of space actually available might differ from the value assigned. In some cases, the amount might be less than the value assigned. It is also possible that the server will adjust a value upward. For example, if you assign a value of 0 to an option for which the minimal value is 1024, the server will set the value to 1024.

Values for buffer sizes, lengths, and stack sizes are given in bytes unless otherwise specified.

Some options take file name values. Unless otherwise specified, the default file location is the data directory if the value is a relative path name. To specify the location explicitly, use an absolute path name. Suppose that the data directory is /var/mysql/data. If a file-valued option is given as a relative path name, it will be located under /var/mysql/data. If the value is an absolute path name, its location is as given by the path name.

  • --help, -?

    Command-Line Format--help

    Display a short help message and exit. Use both the --verbose and --help options to see the full message.

  • --allow-suspicious-udfs

    Command-Line Format--allow-suspicious-udfs
    Permitted ValuesTypeboolean
    DefaultFALSE

    This option controls whether user-defined functions that have only an xxx symbol for the main function can be loaded. By default, the option is off and only UDFs that have at least one auxiliary symbol can be loaded; this prevents attempts at loading functions from shared object files other than those containing legitimate UDFs. See Section 24.3.2.6, “User-Defined Function Security Precautions”.

  • --ansi

    Command-Line Format--ansi

    Use standard (ANSI) SQL syntax instead of MySQL syntax. For more precise control over the server SQL mode, use the --sql-mode option instead. See Section 1.8, “MySQL Standards Compliance”, and Section 5.1.7, “Server SQL Modes”.

  • --basedir=path, -b path

    Command-Line Format--basedir=path
    System VariableNamebasedir
    Variable ScopeGlobal
    Dynamic VariableNo
    Permitted ValuesTypedirectory name

    The path to the MySQL installation directory. All paths are usually resolved relative to this directory.

  • --big-tables

    Command-Line Format--big-tables
    System VariableNamebig_tables
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Permitted ValuesTypeboolean
    DefaultOFF

    Enable large result sets by saving all temporary sets in files. This option prevents most table full errors, but also slows down queries for which in-memory tables would suffice. Since MySQL 3.23.2, the server is able to handle large result sets automatically by using memory for small temporary tables and switching to disk tables where necessary.

  • --bind-address=addr

    Command-Line Format--bind-address=addr
    System Variable (>= 5.6.1)Namebind_address
    Variable ScopeGlobal
    Dynamic VariableNo
    Permitted Values (<= 5.6.5)Typestring
    Default0.0.0.0
    Permitted Values (>= 5.6.6)Typestring
    Default*

    The MySQL server listens on a single network socket for TCP/IP connections. This socket is bound to a single address, but it is possible for an address to map onto multiple network interfaces. To specify an address, use the --bind-address=addr option at server startup, where addr is an IPv4 or IPv6 address or a host name. If addr is a host name, the server resolves the name to an IP address and binds to that address.

    The server treats different types of addresses as follows:

    • If the address is *, the server accepts TCP/IP connections on all server host IPv6 and IPv4 interfaces if the server host supports IPv6, or accepts TCP/IP connections on all IPv4 addresses otherwise. Use this address to permit both IPv4 and IPv6 connections on all server interfaces. This value is permitted (and is the default) as of MySQL 5.6.6.

    • If the address is 0.0.0.0, the server accepts TCP/IP connections on all server host IPv4 interfaces. This is the default before MySQL 5.6.6.

    • If the address is ::, the server accepts TCP/IP connections on all server host IPv4 and IPv6 interfaces.

    • If the address is an IPv4-mapped address, the server accepts TCP/IP connections for that address, in either IPv4 or IPv6 format. For example, if the server is bound to ::ffff:127.0.0.1, clients can connect using --host=127.0.0.1 or --host=::ffff:127.0.0.1.

    • If the address is a regular IPv4 or IPv6 address (such as 127.0.0.1 or ::1), the server accepts TCP/IP connections only for that IPv4 or IPv6 address.

    If you intend to bind the server to a specific address, be sure that the mysql.user grant table contains an account with administrative privileges that you can use to connect to that address. Otherwise, you will not be able to shut down the server. For example, if you bind the server to *, you can connect to it using all existing accounts. But if you bind the server to ::1, it accepts connections only on that address. In that case, first make sure that the 'root'@'::1' account is present in the mysql.user table so you can still connect to the server to shut it down.

  • --binlog-format={ROW|STATEMENT|MIXED}

    Command-Line Format--binlog-format=format
    System VariableNamebinlog_format
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Permitted ValuesTypeenumeration
    DefaultSTATEMENT
    Valid ValuesROW
    STATEMENT
    MIXED
    Permitted ValuesTypeenumeration
    DefaultMIXED
    Valid ValuesROW
    STATEMENT
    MIXED
    Permitted ValuesTypeenumeration
    DefaultMIXED
    Valid ValuesROW
    STATEMENT
    MIXED
    Permitted ValuesTypeenumeration
    DefaultMIXED
    Valid ValuesROW
    STATEMENT
    MIXED
    Permitted ValuesTypeenumeration
    DefaultMIXED
    Valid ValuesROW
    STATEMENT
    MIXED
    Permitted ValuesTypeenumeration
    DefaultMIXED
    Valid ValuesROW
    STATEMENT
    MIXED

    Specify whether to use row-based, statement-based, or mixed replication. Statement-based is the default in MySQL 5.6. See Section 17.1.2, “Replication Formats”.

    Under some conditions, changing this variable at runtime is not possible, or causes replication to fail. See Section 5.2.4.2, “Setting The Binary Log Format”, for more information.

    Setting the binary logging format without enabling binary logging sets the binlog_format global system variable and logs a warning.

  • --bootstrap

    Command-Line Format--bootstrap

    This option is used by the mysql_install_db program to create the MySQL privilege tables without having to start a full MySQL server.

    In MySQL 5.6.6 and later, replication and global transaction identifiers are automatically disabled whenever this option is used (Bug #1332602). See Section 17.1.3, “Replication with Global Transaction Identifiers”.

  • --character-sets-dir=path

    Command-Line Format--character-sets-dir=path
    System VariableNamecharacter_sets_dir
    Variable ScopeGlobal
    Dynamic VariableNo
    Permitted ValuesTypedirectory name

    The directory where character sets are installed. See Section 10.5, “Character Set Configuration”.

  • --character-set-client-handshake

    Command-Line Format--character-set-client-handshake
    Permitted ValuesTypeboolean
    DefaultTRUE

    Do not ignore character set information sent by the client. To ignore client information and use the default server character set, use --skip-character-set-client-handshake; this makes MySQL behave like MySQL 4.0.

  • --character-set-filesystem=charset_name

    Command-Line Format--character-set-filesystem=name
    System VariableNamecharacter_set_filesystem
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Permitted ValuesTypestring
    Defaultbinary

    The file system character set. This option sets the character_set_filesystem system variable.

  • --character-set-server=charset_name, -C charset_name

    Command-Line Format--character-set-server
    System VariableNamecharacter_set_server
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Permitted ValuesTypestring
    Defaultlatin1

    Use charset_name as the default server character set. See Section 10.5, “Character Set Configuration”. If you use this option to specify a nondefault character set, you should also use --collation-server to specify the collation.

  • --chroot=path, -r path

    Command-Line Format--chroot=dir_name
    Permitted ValuesTypedirectory name

    Put the mysqld server in a closed environment during startup by using the chroot() system call. This is a recommended security measure. Note that use of this option somewhat limits LOAD DATA INFILE and SELECT ... INTO OUTFILE.

  • --collation-server=collation_name

    Command-Line Format--collation-server
    System VariableNamecollation_server
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Permitted ValuesTypestring
    Defaultlatin1_swedish_ci

    Use collation_name as the default server collation. See Section 10.5, “Character Set Configuration”.

  • --console

    Command-Line Format--console
    Platform SpecificWindows

    (Windows only.) Write error log messages to stderr and stdout. mysqld does not close the console window if this option is used.

    If both --log-error and --console are specified, --log-error takes precedence. The server writes to the log file, but not to the console.

  • --core-file

    Command-Line Format--core-file
    Permitted ValuesTypeboolean
    DefaultOFF

    Write a core file if mysqld dies. The name and location of the core file is system dependent. On Linux, a core file named core.pid is written to the current working directory of the process, which for mysqld is the data directory. pid represents the process ID of the server process. On OS X, a core file named core.pid is written to the /cores directory. On Solaris, use the coreadm command to specify where to write the core file and how to name it.

    For some systems, to get a core file you must also specify the --core-file-size option to mysqld_safe. See Section 4.3.2, “mysqld_safe — MySQL Server Startup Script”. On some systems, such as Solaris, you do not get a core file if you are also using the --user option. There might be additional restrictions or limitations. For example, it might be necessary to execute ulimit -c unlimited before starting the server. Consult your system documentation.

  • --datadir=path, -h path

    Command-Line Format--datadir=path
    System VariableNamedatadir
    Variable ScopeGlobal
    Dynamic VariableNo
    Permitted ValuesTypedirectory name

    The path to the data directory.

  • --debug[=debug_options], -# [debug_options]

    Command-Line Format--debug[=debug_options]
    System VariableNamedebug
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Permitted Values (Unix)Typestring
    Defaultd:t:i:o,/tmp/mysqld.trace
    Permitted Values (Windows)Typestring
    Defaultd:t:i:O,\mysqld.trace

    If MySQL is configured with -DWITH_DEBUG=1, you can use this option to get a trace file of what mysqld is doing. A typical debug_options string is d:t:o,file_name. The default is d:t:i:o,/tmp/mysqld.trace on Unix and d:t:i:O,\mysqld.trace on Windows.

    Using -DWITH_DEBUG=1 to configure MySQL with debugging support enables you to use the --debug="d,parser_debug" option when you start the server. This causes the Bison parser that is used to process SQL statements to dump a parser trace to the server's standard error output. Typically, this output is written to the error log.

    This option may be given multiple times. Values that begin with + or - are added to or subtracted from the previous value. For example, --debug=T --debug=+P sets the value to P:T.

    For more information, see Section 24.4.3, “The DBUG Package”.

  • --debug-sync-timeout[=N]

    Command-Line Format--debug-sync-timeout[=#]
    Permitted ValuesTypenumeric

    Controls whether the Debug Sync facility for testing and debugging is enabled. Use of Debug Sync requires that MySQL be configured with the -DENABLE_DEBUG_SYNC=1 option (see Section 2.9.4, “MySQL Source-Configuration Options”). If Debug Sync is not compiled in, this option is not available. The option value is a timeout in seconds. The default value is 0, which disables Debug Sync. To enable it, specify a value greater than 0; this value also becomes the default timeout for individual synchronization points. If the option is given without a value, the timeout is set to 300 seconds.

    For a description of the Debug Sync facility and how to use synchronization points, see MySQL Internals: Test Synchronization.

  • --default-authentication-plugin=plugin_name

    Introduced5.6.6
    Command-Line Format--default-authentication-plugin=plugin_name
    Permitted ValuesTypeenumeration
    Defaultmysql_native_password
    Valid Valuesmysql_native_password
    sha256_password

    This option sets the default authentication plugin. Permitted values are mysql_native_password (use MySQL native passwords) and sha256_password (use SHA-256 passwords). For more information about these plugins, see Section 6.3.8.1, “The Native Authentication Plugin”, and Section 6.3.8.4, “The SHA-256 Authentication Plugin”. This option was added in MySQL 5.6.6.

    Note

    Prior to MySQL 5.6.17, if you use this option to change the default authentication plugin to a value other than mysql_native_password, clients older than MySQL 5.5.7 cannot connect because they do not understand the resulting change to the authentication protocol.

    In MySQL 5.6, there is no server system variable that corresponds to the --default-authentication-plugin option; to read the value set for this option, you must check the running MySQL Server process to see what options, if any, were employed when invoking mysqld (on Linux systems, you can do this with ps ax | grep mysqld or similar), and possibly the server options file as well. This is a known issue which is resolved in MySQL 5.7. (Bug #68858, Bug #16595944)

    The --default-authentication-plugin value affects these aspects of server operation:

    • It determines which authentication plugin the server assigns to new accounts created by CREATE USER and GRANT statements that do not name a plugin explicitly with an IDENTIFIED WITH clause.

    • It sets the old_passwords system variable at startup to the value that is consistent with the password hashing method required by the default plugin. The old_passwords value affects hashing of passwords specified in the IDENTIFIED BY clause of CREATE USER and GRANT, and passwords specified as the argument to the PASSWORD() function.

    • For an account created with either of the following statements, the server associates the account with the default authentication plugin and assigns the account the given password, hashed according to the value of old_passwords.

      CREATE USER ... IDENTIFIED BY 'cleartext password';
      GRANT ...  IDENTIFIED BY 'cleartext password';
      
    • For an account created with either of the following statements, the statement fails if the password hash is not encrypted using the hash format required by the default authentication plugin. Otherwise, the server associates the account with the default authentication plugin and assigns the account the given password hash.

      CREATE USER ... IDENTIFIED BY PASSWORD 'encrypted password';
      GRANT ...  IDENTIFIED BY PASSWORD 'encrypted password';
      
  • --default-storage-engine=type

    Command-Line Format--default-storage-engine=name
    System VariableNamedefault_storage_engine
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Permitted ValuesTypeenumeration
    DefaultInnoDB

    Set the default storage engine for tables. See Chapter 15, Alternative Storage Engines. As of MySQL 5.6.3, this option sets the storage engine for permanent tables only. To set the storage engine for TEMPORARY tables, set the default_tmp_storage_engine system variable.

    If you disable the default storage engine at server startup, you must set the default engine for both permanent and TEMPORARY tables to a different engine or the server will not start.

  • --default-time-zone=timezone

    Command-Line Format--default-time-zone=name
    Permitted ValuesTypestring

    Set the default server time zone. This option sets the global time_zone system variable. If this option is not given, the default time zone is the same as the system time zone (given by the value of the system_time_zone system variable.

  • --defaults-extra-file=file_name

    Read this option file after the global option file but (on Unix) before the user option file. If the file does not exist or is otherwise inaccessible, an error occurs. file_name is interpreted relative to the current directory if given as a relative path name rather than a full path name.

  • --defaults-file=file_name

    Use only the given option file. If the file does not exist or is otherwise inaccessible, an error occurs. file_name is interpreted relative to the current directory if given as a relative path name rather than a full path name.

  • --defaults-group-suffix=str

    Read not only the usual option groups, but also groups with the usual names and a suffix of str. For example, mysqld normally reads the [mysqld] group. If the --defaults-group-suffix=_other option is given, mysqld also reads the [mysqld_other] group.

  • --delay-key-write[={OFF|ON|ALL}]

    Command-Line Format--delay-key-write[=name]
    System VariableNamedelay_key_write
    Variable ScopeGlobal
    Dynamic VariableYes
    Permitted ValuesTypeenumeration
    DefaultON
    Valid ValuesON
    OFF
    ALL

    Specify how to use delayed key writes. Delayed key writing causes key buffers not to be flushed between writes for MyISAM tables. OFF disables delayed key writes. ON enables delayed key writes for those tables that were created with the DELAY_KEY_WRITE option. ALL delays key writes for all MyISAM tables. See Section 8.11.2, “Tuning Server Parameters”, and Section 15.2.1, “MyISAM Startup Options”.

    Note

    If you set this variable to ALL, you should not use MyISAM tables from within another program (such as another MySQL server or myisamchk) when the tables are in use. Doing so leads to index corruption.

  • --des-key-file=file_name

    Command-Line Format--des-key-file=file_name

    Read the default DES keys from this file. These keys are used by the DES_ENCRYPT() and DES_DECRYPT() functions.

  • --enable-named-pipe

    Command-Line Format--enable-named-pipe
    Platform SpecificWindows

    Enable support for named pipes. This option applies only on Windows.

  • --engine-condition-pushdown={ON|OFF}

    Deprecated5.5.3, by optimizer_switch
    Removed5.6.1
    Command-Line Format--engine-condition-pushdown
    System VariableNameengine_condition_pushdown
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Permitted ValuesTypeboolean
    DefaultON

    Formerly, this option set the engine_condition_pushdown system variable; the option and the variable were both removed in MySQL 5.6.1. For more information, see Section 8.2.1.5, “Engine Condition Pushdown Optimization”.

  • --event-scheduler[=value]

    Command-Line Format--event-scheduler[=value]
    System VariableNameevent_scheduler
    Variable ScopeGlobal
    Dynamic VariableYes
    Permitted ValuesTypeenumeration
    DefaultOFF
    Valid ValuesON
    OFF
    DISABLED

    Enable or disable, and start or stop, the event scheduler.

    For detailed information, see The --event-scheduler Option.

  • --exit-info[=flags], -T [flags]

    Command-Line Format--exit-info[=flags]
    Permitted ValuesTypenumeric

    This is a bit mask of different flags that you can use for debugging the mysqld server. Do not use this option unless you know exactly what it does!

  • --external-locking

    Command-Line Format--external-locking
    Permitted ValuesTypeboolean
    DefaultFALSE

    Enable external locking (system locking), which is disabled by default as of MySQL 4.0. Note that if you use this option on a system on which lockd does not fully work (such as Linux), it is easy for mysqld to deadlock.

    To disable external locking explicitly, use --skip-external-locking.

    External locking affects only MyISAM table access. For more information, including conditions under which it can and cannot be used, see Section 8.10.5, “External Locking”.

  • --flush

    Command-Line Format--flush
    System VariableNameflush
    Variable ScopeGlobal
    Dynamic VariableYes
    Permitted ValuesTypeboolean
    DefaultOFF

    Flush (synchronize) all changes to disk after each SQL statement. Normally, MySQL does a write of all changes to disk only after each SQL statement and lets the operating system handle the synchronizing to disk. See Section B.5.4.2, “What to Do If MySQL Keeps Crashing”.

  • --gdb

    Command-Line Format--gdb
    Permitted ValuesTypeboolean
    DefaultFALSE

    Install an interrupt handler for SIGINT (needed to stop mysqld with ^C to set breakpoints) and disable stack tracing and core file handling. See Section 24.4, “Debugging and Porting MySQL”.

  • --general-log[={0|1}]

    Command-Line Format--general-log
    System VariableNamegeneral_log
    Variable ScopeGlobal
    Dynamic VariableYes
    Permitted ValuesTypeboolean
    DefaultOFF

    Specify the initial general query log state. With no argument or an argument of 1, the --general-log option enables the log. If omitted or given with an argument of 0, the option disables the log.

  • --ignore-db-dir=dir_name

    Introduced5.6.3
    Command-Line Format--ignore-db-dir
    Permitted ValuesTypedirectory name

    This option tells the server to ignore the given directory name for purposes of the SHOW DATABASES statement or INFORMATION_SCHEMA tables. For example, if a MySQL configuration locates the data directory at the root of a file system on Unix, the system might create a lost+found directory there that the server should ignore. Starting the server with --ignore-db-dir=lost+found causes that name not to be listed as a database.

    To specify more than one name, use this option multiple times, once for each name. Specifying the option with an empty value (that is, as --ignore-db-dir=) resets the directory list to the empty list.

    Instances of this option given at server startup are used to set the ignore_db_dirs system variable.

    This option was added in MySQL 5.6.3.

  • --init-file=file_name

    Command-Line Format--init-file=file_name
    System VariableNameinit_file
    Variable ScopeGlobal
    Dynamic VariableNo
    Permitted ValuesTypefile name

    Read SQL statements from this file at startup. Each statement must be on a single line and should not include comments.

  • --innodb-xxx

    Set an option for the InnoDB storage engine. The InnoDB options are listed in Section 14.12, “InnoDB Startup Options and System Variables”.

  • --install [service_name]

    Command-Line Format--install [service_name]
    Platform SpecificWindows

    (Windows only) Install the server as a Windows service that starts automatically during Windows startup. The default service name is MySQL if no service_name value is given. For more information, see Section 2.3.5.7, “Starting MySQL as a Windows Service”.

    Note

    If the server is started with the --defaults-file and --install options, --install must be first.

  • --install-manual [service_name]

    Command-Line Format--install-manual [service_name]
    Platform SpecificWindows

    (Windows only) Install the server as a Windows service that must be started manually. It does not start automatically during Windows startup. The default service name is MySQL if no service_name value is given. For more information, see Section 2.3.5.7, “Starting MySQL as a Windows Service”.

    Note

    If the server is started with the --defaults-file and --install-manual options, --install-manual must be first.

  • --language=lang_name, -L lang_name

    Deprecated5.6.1, by lc-messages-dir
    Command-Line Format--language=name
    System VariableNamelanguage
    Variable ScopeGlobal
    Dynamic VariableNo
    Permitted ValuesTypedirectory name
    Default/usr/local/mysql/share/mysql/english/

    The language to use for error messages. lang_name can be given as the language name or as the full path name to the directory where the language files are installed. See Section 10.2, “Setting the Error Message Language”.

    In MySQL 5.6, --lc-messages-dir and --lc-messages should be used rather than --language, which is deprecated as of MySQL 5.6.1 and handled as an alias for --lc-messages-dir. The --language option will be removed in a future MySQL release.

  • --large-pages

    Command-Line Format--large-pages
    System VariableNamelarge_pages
    Variable ScopeGlobal
    Dynamic VariableNo
    Platform SpecificLinux
    Permitted Values (Linux)Typeboolean
    DefaultFALSE

    Some hardware/operating system architectures support memory pages greater than the default (usually 4KB). The actual implementation of this support depends on the underlying hardware and operating system. Applications that perform a lot of memory accesses may obtain performance improvements by using large pages due to reduced Translation Lookaside Buffer (TLB) misses.

    MySQL 5.6 supports the Linux implementation of large page support (which is called HugeTLB in Linux). See Section 8.11.4.2, “Enabling Large Page Support”. For Solaris support of large pages, see the description of the --super-large-pages option.

    --large-pages is disabled by default.

  • --lc-messages=locale_name

    Command-Line Format--lc-messages=name
    System VariableNamelc_messages
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Permitted ValuesTypestring
    Defaulten_US

    The locale to use for error messages. The default is en_US. The server converts the argument to a language name and combines it with the value of --lc-messages-dir to produce the location for the error message file. See Section 10.2, “Setting the Error Message Language”.

  • --lc-messages-dir=path

    Command-Line Format--lc-messages-dir=dir_name
    System VariableNamelc_messages_dir
    Variable ScopeGlobal
    Dynamic VariableNo
    Permitted ValuesTypedirectory name

    The directory where error messages are located. The server uses the value together with the value of --lc-messages to produce the location for the error message file. See Section 10.2, “Setting the Error Message Language”.

  • --local-service

    Command-Line Format--local-service

    (Windows only) A --local-service option following the service name causes the server to run using the LocalService Windows account that has limited system privileges. This account is available only for Windows XP or newer. If both --defaults-file and --local-service are given following the service name, they can be in any order. See Section 2.3.5.7, “Starting MySQL as a Windows Service”.

  • --log[=file_name], -l [file_name]

    Deprecated5.1.29, by general-log
    Removed5.6.1
    Command-Line Format--log[=file_name]
    System VariableNamelog
    Variable ScopeGlobal
    Dynamic VariableYes
    Permitted ValuesTypefile name

    The --log option was removed in MySQL 5.6.1 (along with the log system variable). Instead, use the --general_log option to enable the general query log and the --general_log_file=file_name option to set the general query log file name.

  • --log-error[=file_name]

    Command-Line Format--log-error[=file_name]
    System VariableNamelog_error
    Variable ScopeGlobal
    Dynamic VariableNo
    Permitted ValuesTypefile name

    Log errors and startup messages to this file. See Section 5.2.2, “The Error Log”. If you omit the file name, MySQL uses host_name.err. If the file name has no extension, the server adds an extension of .err.

  • --log-isam[=file_name]

    Command-Line Format--log-isam[=file_name]
    Permitted ValuesTypefile name

    Log all MyISAM changes to this file (used only when debugging MyISAM).

  • --log-output=value,...

    Command-Line Format--log-output=name
    System VariableNamelog_output
    Variable ScopeGlobal
    Dynamic VariableYes
    Permitted ValuesTypeset
    DefaultFILE
    Valid ValuesTABLE
    FILE
    NONE

    This option determines the destination for general query log and slow query log output. The option value can be given as one or more of the words TABLE, FILE, or NONE. TABLE select logging to the general_log and slow_log tables in the mysql database as a destination. FILE selects logging to log files as a destination. NONE disables logging. If NONE is present in the option value, it takes precedence over any other words that are present. TABLE and FILE can both be given to select to both log output destinations.

    This option selects log output destinations, but does not enable log output. To do that, use the --general_log and --slow_query_log options. For FILE logging, the --general_log_file and -slow_query_log_file options determine the log file location. For more information, see Section 5.2.1, “Selecting General Query and Slow Query Log Output Destinations”.

  • --log-queries-not-using-indexes

    Command-Line Format--log-queries-not-using-indexes
    System VariableNamelog_queries_not_using_indexes
    Variable ScopeGlobal
    Dynamic VariableYes
    Permitted ValuesTypeboolean
    DefaultOFF

    If you are using this option with the slow query log enabled, queries that are expected to retrieve all rows are logged. See Section 5.2.5, “The Slow Query Log”. This option does not necessarily mean that no index is used. For example, a query that uses a full index scan uses an index but would be logged because the index would not limit the number of rows.

  • --log-raw

    Introduced5.6.3
    Command-Line Format--log-raw[=value]
    Permitted ValuesTypeboolean
    DefaultOFF

    As of MySQL 5.6.3, passwords in certain statements written to the general query log, slow query log, and binary log are rewritten by the server not to occur literally in plain text. Password rewriting can be suppressed for the general query log by starting the server with the --log-raw option. This option may be useful for diagnostic purposes, to see the exact text of statements as received by the server, but for security reasons is not recommended for production use.

    Before MySQL 5.6.3, passwords in statements are not rewritten and the general query log should be protected. See Section 6.1.2.3, “Passwords and Logging”.

    This option was added in MySQL 5.6.3.

  • --log-short-format

    Command-Line Format--log-short-format
    Permitted ValuesTypeboolean
    DefaultFALSE

    Log less information to the binary log and slow query log, if they have been activated.

  • --log-slow-admin-statements

    Removed5.6.11
    Command-Line Format--log-slow-admin-statements (<= 5.6.10)
    Permitted ValuesTypeboolean
    DefaultOFF

    Include slow administrative statements in the statements written to the slow query log. Administrative statements include ALTER TABLE, ANALYZE TABLE, CHECK TABLE, CREATE INDEX, DROP INDEX, OPTIMIZE TABLE, and REPAIR TABLE.

    This command-line option was removed in MySQL 5.6.11 and replaced by the log_slow_admin_statements system variable. The system variable can be set on the command line or in option files the same way as the option, so there is no need for any changes at server startup, but the system variable also makes it possible to examine or set the value at runtime.

  • --log-slow-queries[=file_name]

    Deprecated5.1.29, by slow-query-log
    Removed5.6.1
    Command-Line Format--log-slow-queries[=name]
    System VariableNamelog_slow_queries
    Variable ScopeGlobal
    Dynamic VariableYes
    Permitted ValuesTypeboolean

    The --log-slow-queries option was removed in MySQL 5.6.1 (along with the log_slow_queries system variable). Instead, use the --slow_query_log option to enable the slow query log and the --slow_query_log_file=file_name option to set the slow query log file name.

  • --log-tc=file_name

    Command-Line Format--log-tc=file_name
    Permitted ValuesTypefile name
    Defaulttc.log

    The name of the memory-mapped transaction coordinator log file (for XA transactions that affect multiple storage engines when the binary log is disabled). The default name is tc.log. The file is created under the data directory if not given as a full path name. Currently, this option is unused.

  • --log-tc-size=size

    Command-Line Format--log-tc-size=#
    Permitted Values (32-bit platforms)Typenumeric
    Default24576
    Max Value4294967295
    Permitted Values (64-bit platforms)Typenumeric
    Default24576
    Max Value18446744073709551615

    The size in bytes of the memory-mapped transaction coordinator log. The default size is 24KB.

  • --log-warnings[=level], -W [level]

    Command-Line Format--log-warnings[=#]
    System Variable (<= 5.6.3)Namelog_warnings
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    System Variable (>= 5.6.4)Namelog_warnings
    Variable ScopeGlobal
    Dynamic VariableYes
    Permitted Values (32-bit platforms)Typenumeric
    Default1
    Min Value0
    Max Value4294967295
    Permitted Values (64-bit platforms)Typenumeric
    Default1
    Min Value0
    Max Value18446744073709551615

    Print out warnings such as Aborted connection... to the error log. This option is enabled (1) by default. To disable it, use --log-warnings=0. Specifying the option without a level value increments the current value by 1. Enabling this option by setting it greater than 0 is recommended, for example, if you use replication (you get more information about what is happening, such as messages about network failures and reconnections). If the value is greater than 1, aborted connections are written to the error log, and access-denied errors for new connection attempts are written. See Section B.5.2.11, “Communication Errors and Aborted Connections”.

    If a slave server was started with --log-warnings enabled, the slave prints messages to the error log to provide information about its status, such as the binary log and relay log coordinates where it starts its job, when it is switching to another relay log, when it reconnects after a disconnect, and so forth. The server logs messages about statements that are unsafe for statement-based logging if --log-warnings is greater than 0.

  • --low-priority-updates

    Command-Line Format--low-priority-updates
    System VariableNamelow_priority_updates
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Permitted ValuesTypeboolean
    DefaultFALSE

    Give table-modifying operations (INSERT, REPLACE, DELETE, UPDATE) lower priority than selects. This can also be done using {INSERT | REPLACE | DELETE | UPDATE} LOW_PRIORITY ... to lower the priority of only one query, or by SET LOW_PRIORITY_UPDATES=1 to change the priority in one thread. This affects only storage engines that use only table-level locking (MyISAM, MEMORY, MERGE). See Section 8.10.2, “Table Locking Issues”.

  • --min-examined-row-limit=number

    Command-Line Format--min-examined-row-limit=#
    System VariableNamemin_examined_row_limit
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Permitted Values (32-bit platforms)Typenumeric
    Default0
    Min Value0
    Max Value4294967295
    Permitted Values (64-bit platforms)Typenumeric
    Default0
    Min Value0
    Max Value18446744073709551615

    When this option is set, queries which examine fewer than number rows are not written to the slow query log. The default is 0.

  • --memlock

    Command-Line Format--memlock
    Permitted ValuesTypeboolean
    DefaultFALSE

    Lock the mysqld process in memory. This option might help if you have a problem where the operating system is causing mysqld to swap to disk.

    --memlock works on systems that support the mlockall() system call; this includes Solaris, most Linux distributions that use a 2.4 or newer kernel, and perhaps other Unix systems. On Linux systems, you can tell whether or not mlockall() (and thus this option) is supported by checking to see whether or not it is defined in the system mman.h file, like this:

    shell> grep mlockall /usr/include/sys/mman.h
    

    If mlockall() is supported, you should see in the output of the previous command something like the following:

    extern int mlockall (int __flags) __THROW;
    
    Important

    Use of this option may require you to run the server as root, which, for reasons of security, is normally not a good idea. See Section 6.1.5, “How to Run MySQL as a Normal User”.

    On Linux and perhaps other systems, you can avoid the need to run the server as root by changing the limits.conf file. See the notes regarding the memlock limit in Section 8.11.4.2, “Enabling Large Page Support”.

    You must not try to use this option on a system that does not support the mlockall() system call; if you do so, mysqld will very likely crash as soon as you try to start it.

  • --myisam-block-size=N

    Command-Line Format--myisam-block-size=#
    Permitted ValuesTypenumeric
    Default1024
    Min Value1024
    Max Value16384

    The block size to be used for MyISAM index pages.

  • --myisam-recover-options[=option[,option]...]]

    Command-Line Format--myisam-recover-options[=name]
    Permitted ValuesTypeenumeration
    DefaultOFF
    Valid ValuesOFF
    DEFAULT
    BACKUP
    FORCE
    QUICK

    Set the MyISAM storage engine recovery mode. The option value is any combination of the values of OFF, DEFAULT, BACKUP, FORCE, or QUICK. If you specify multiple values, separate them by commas. Specifying the option with no argument is the same as specifying DEFAULT, and specifying with an explicit value of "" disables recovery (same as a value of OFF). If recovery is enabled, each time mysqld opens a MyISAM table, it checks whether the table is marked as crashed or was not closed properly. (The last option works only if you are running with external locking disabled.) If this is the case, mysqld runs a check on the table. If the table was corrupted, mysqld attempts to repair it.

    The following options affect how the repair works.

    OptionDescription
    OFFNo recovery.
    DEFAULTRecovery without backup, forcing, or quick checking.
    BACKUPIf the data file was changed during recovery, save a backup of the tbl_name.MYD file as tbl_name-datetime.BAK.
    FORCERun recovery even if we would lose more than one row from the .MYD file.
    QUICKDo not check the rows in the table if there are not any delete blocks.

    Before the server automatically repairs a table, it writes a note about the repair to the error log. If you want to be able to recover from most problems without user intervention, you should use the options BACKUP,FORCE. This forces a repair of a table even if some rows would be deleted, but it keeps the old data file as a backup so that you can later examine what happened.

    See Section 15.2.1, “MyISAM Startup Options”.

  • --no-defaults

    Do not read any option files. If program startup fails due to reading unknown options from an option file, --no-defaults can be used to prevent them from being read.

    The exception is that the .mylogin.cnf file, if it exists, is read in all cases. This permits passwords to be specified in a safer way than on the command line even when --no-defaults is used. (.mylogin.cnf is created by the mysql_config_editor utility. See Section 4.6.6, “mysql_config_editor — MySQL Configuration Utility”.)

  • --old-alter-table

    Command-Line Format--old-alter-table
    System VariableNameold_alter_table
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Permitted ValuesTypeboolean
    DefaultOFF

    When this option is given, the server does not use the optimized method of processing an ALTER TABLE operation. It reverts to using a temporary table, copying over the data, and then renaming the temporary table to the original, as used by MySQL 5.0 and earlier. For more information on the operation of ALTER TABLE, see Section 13.1.7, “ALTER TABLE Syntax”.

  • --old-style-user-limits

    Command-Line Format--old-style-user-limits
    Permitted ValuesTypeboolean
    DefaultFALSE

    Enable old-style user limits. (Before MySQL 5.0.3, account resource limits were counted separately for each host from which a user connected rather than per account row in the user table.) See Section 6.3.4, “Setting Account Resource Limits”.

  • --one-thread

    Removed5.6.1
    Command-Line Format--one-thread

    This option was removed in MySQL 5.6.1. Use --thread_handling=no-threads instead.

  • --open-files-limit=count

    Command-Line Format--open-files-limit=#
    System VariableNameopen_files_limit
    Variable ScopeGlobal
    Dynamic VariableNo
    Permitted Values (<= 5.6.7)Typenumeric
    Default0
    Min Value0
    Max Valueplatform dependent
    Permitted Values (>= 5.6.8)Typenumeric
    Default5000, with possible adjustment
    Min Value0
    Max Valueplatform dependent

    Changes the number of file descriptors available to mysqld. You should try increasing the value of this option if mysqld gives you the error Too many open files. mysqld uses the option value to reserve descriptors with setrlimit(). Internally, the maximum value for this option is the maximum unsigned integer value, but the actual maximum is platform dependent. If the requested number of file descriptors cannot be allocated, mysqld writes a warning to the error log.

    mysqld may attempt to allocate more than the requested number of descriptors (if they are available), using the values of max_connections and table_open_cache to estimate whether more descriptors will be needed.

    On Unix, the value cannot be set less than ulimit -n.

  • --partition[=value]

    Command-Line Format--partition
    Disabled byskip-partition
    Permitted ValuesTypeboolean
    DefaultON

    Enables or disables user-defined partitioning support in the MySQL Server.

  • --performance-schema-xxx

    Configure a Performance Schema option. For details, see Section 22.11, “Performance Schema Command Options”.

  • --pid-file=path

    Command-Line Format--pid-file=file_name
    System VariableNamepid_file
    Variable ScopeGlobal
    Dynamic VariableNo
    Permitted ValuesTypefile name

    The path name of the process ID file. The server creates the file in the data directory unless an absolute path name is given to specify a different directory. This file is used by other programs such as mysqld_safe to determine the server's process ID.

  • --plugin-xxx

    Specifies an option that pertains to a server plugin. For example, many storage engines can be built as plugins, and for such engines, options for them can be specified with a --plugin prefix. Thus, the --innodb_file_per_table option for InnoDB can be specified as --plugin-innodb_file_per_table.

    For boolean options that can be enabled or disabled, the --skip prefix and other alternative formats are supported as well (see Section 4.2.5, “Program Option Modifiers”). For example, --skip-plugin-innodb_file_per_table disables innodb_file_per_table.

    The rationale for the --plugin prefix is that it enables plugin options to be specified unambiguously if there is a name conflict with a built-in server option. For example, were a plugin writer to name a plugin sql and implement a mode option, the option name might be --sql-mode, which would conflict with the built-in option of the same name. In such cases, references to the conflicting name are resolved in favor of the built-in option. To avoid the ambiguity, users can specify the plugin option as --plugin-sql-mode. Use of the --plugin prefix for plugin options is recommended to avoid any question of ambiguity.

  • --plugin-load=plugin_list

    Command-Line Format--plugin-load=plugin_list
    Permitted ValuesTypestring

    This option tells the server to load the named plugins at startup. The option value is a semicolon-separated list of name=plugin_library pairs. Each name is the name of the plugin, and plugin_library is the name of the shared library that contains the plugin code. Each library file must be located in the directory named by the plugin_dir system variable. For example, if plugins named myplug1 and myplug2 have library files myplug1.so and myplug2.so, use this option to load them at startup:

    shell> mysqld --plugin-load="myplug1=myplug1.so;myplug2=myplug2.so"
    

    Quotes are used around the argument value here because semicolon (;) is interpreted as a special character by some command interpreters. (Unix shells treat it as a command terminator, for example.)

    If multiple --plugin-load options are given, only the last one is used. Additional plugins to load may be specified using --plugin-load-add options.

    If a plugin library is named without any preceding plugin name, the server loads all plugins in the library.

    Each plugin is loaded for a single invocation of mysqld only. After a restart, the plugin is not loaded unless --plugin-load is used again. This is in contrast to INSTALL PLUGIN, which adds an entry to the mysql.plugins table to cause the plugin to be loaded for every normal server startup.

    Under normal startup, the server determines which plugins to load by reading the mysql.plugins system table. If the server is started with the --skip-grant-tables option, it does not consult the mysql.plugins table and does not load plugins listed there. --plugin-load enables plugins to be loaded even when --skip-grant-tables is given. --plugin-load also enables plugins to be loaded at startup under configurations when plugins cannot be loaded at runtime.

    For additional information about plugin loading, see Section 5.1.8.1, “Installing and Uninstalling Plugins”.

  • --plugin-load-add=plugin_list

    Introduced5.6.3
    Command-Line Format--plugin-load-add=plugin_list
    Permitted ValuesTypestring

    This option complements the --plugin-load option. --plugin-load-add adds a plugin or plugins to the set of plugins to be loaded at startup. The argument format is the same as for --plugin-load. --plugin-load-add can be used to avoid specifying a large set of plugins as a single long unwieldy --plugin-load argument. This option was added in MySQL 5.6.3.

    --plugin-load-add can be given in the absence of --plugin-load, but any instance of --plugin-load-add that appears before --plugin-load. has no effect because --plugin-load resets the set of plugins to load. In other words, these options:

    --plugin-load=x --plugin-load-add=y
    

    are equivalent to this option:

    --plugin-load="x;y"
    

    But these options:

    --plugin-load-add=y --plugin-load=x
    

    are equivalent to this option:

    --plugin-load=x
    

    For additional information about plugin loading, see Section 5.1.8.1, “Installing and Uninstalling Plugins”.

  • --port=port_num, -P port_num

    Command-Line Format--port=#
    System VariableNameport
    Variable ScopeGlobal
    Dynamic VariableNo
    Permitted ValuesTypenumeric
    Default3306
    Min Value0
    Max Value65535

    The port number to use when listening for TCP/IP connections. On Unix and Unix-like systems, the port number must be 1024 or higher unless the server is started by the root system user.

  • --port-open-timeout=num

    Command-Line Format--port-open-timeout=#
    Permitted ValuesTypenumeric
    Default0

    On some systems, when the server is stopped, the TCP/IP port might not become available immediately. If the server is restarted quickly afterward, its attempt to reopen the port can fail. This option indicates how many seconds the server should wait for the TCP/IP port to become free if it cannot be opened. The default is not to wait.

  • --print-defaults

    Print the program name and all options that it gets from option files.

  • --remove [service_name]

    Command-Line Format--remove [service_name]
    Platform SpecificWindows

    (Windows only) Remove a MySQL Windows service. The default service name is MySQL if no service_name value is given. For more information, see Section 2.3.5.7, “Starting MySQL as a Windows Service”.

  • --safe-mode

    Deprecated5.5.26
    Removed5.6.6
    Command-Line Format--safe-mode

    Skip some optimization stages. This option was removed in MySQL 5.6.6.

  • --safe-user-create

    Command-Line Format--safe-user-create
    Permitted ValuesTypeboolean
    DefaultFALSE

    If this option is enabled, a user cannot create new MySQL users by using the GRANT statement unless the user has the INSERT privilege for the mysql.user table or any column in the table. If you want a user to have the ability to create new users that have those privileges that the user has the right to grant, you should grant the user the following privilege:

    GRANT INSERT(user) ON mysql.user TO 'user_name'@'host_name';
    

    This ensures that the user cannot change any privilege columns directly, but has to use the GRANT statement to give privileges to other users.

  • --secure-auth

    Command-Line Format--secure-auth
    System VariableNamesecure_auth
    Variable ScopeGlobal
    Dynamic VariableYes
    Permitted Values (<= 5.6.4)Typeboolean
    DefaultOFF
    Permitted Values (>= 5.6.5)Typeboolean
    DefaultON

    This option causes the server to block connections by clients that attempt to use accounts that have passwords stored in the old (pre-4.1) format. Use it to prevent all use of passwords employing the old format (and hence insecure communication over the network). Before MySQL 5.6.5, this option is disabled by default. As of MySQL 5.6.5, it is enabled by default; to disable it, use --skip-secure-auth.

    Server startup fails with an error if this option is enabled and the privilege tables are in pre-4.1 format. See Section B.5.2.4, “Client does not support authentication protocol”.

    The mysql client also has a --secure-auth option, which prevents connections to a server if the server requires a password in old format for the client account.

    Note

    Passwords that use the pre-4.1 hashing method are less secure than passwords that use the native password hashing method and should be avoided. Pre-4.1 passwords are deprecated and support for them will be removed in a future MySQL release. Consequently, disabling secure authentication using --skip-secure-auth is also deprecated.

  • --secure-file-priv=path

    Command-Line Format--secure-file-priv=path
    System VariableNamesecure_file_priv
    Variable ScopeGlobal
    Dynamic VariableNo
    Permitted ValuesTypestring

    This option limits the effect of the LOAD_FILE() function and the LOAD DATA and SELECT ... INTO OUTFILE statements to work only with files in the specified directory.

  • --shared-memory

    Command-Line Format--shared-memory-base-name=name
    System VariableNameshared_memory
    Variable ScopeGlobal
    Dynamic VariableNo
    Platform SpecificWindows

    Enable shared-memory connections by local clients. This option is available only on Windows.

  • --shared-memory-base-name=name

    System VariableNameshared_memory_base_name
    Variable ScopeGlobal
    Dynamic VariableNo
    Platform SpecificWindows

    The name of shared memory to use for shared-memory connections. This option is available only on Windows. The default name is MYSQL. The name is case sensitive.

  • --skip-concurrent-insert

    Turn off the ability to select and insert at the same time on MyISAM tables. (This is to be used only if you think you have found a bug in this feature.) See Section 8.10.3, “Concurrent Inserts”.

  • --skip-event-scheduler

    Command-Line Format--skip-event-scheduler
     --disable-event-scheduler

    Turns the Event Scheduler OFF. This is not the same as disabling the Event Scheduler, which requires setting --event-scheduler=DISABLED; see The --event-scheduler Option, for more information.

  • --skip-grant-tables

    This option causes the server to start without using the privilege system at all, which gives anyone with access to the server unrestricted access to all databases. You can cause a running server to start using the grant tables again by executing mysqladmin flush-privileges or mysqladmin reload command from a system shell, or by issuing a MySQL FLUSH PRIVILEGES statement after connecting to the server. This option also suppresses loading of plugins that were installed with the INSTALL PLUGIN statement, user-defined functions (UDFs), and scheduled events. To cause plugins to be loaded anyway, use the --plugin-load option.

    Note that FLUSH PRIVILEGES might be executed implicitly by other actions performed after startup. For example, mysql_upgrade flushes the privileges during the upgrade procedure.

  • --skip-host-cache

    Disable use of the internal host cache for faster name-to-IP resolution. In this case, the server performs a DNS lookup every time a client connects. See Section 8.11.5.2, “DNS Lookup Optimization and the Host Cache”.

    Use of --skip-host-cache is similar to setting the host_cache_size system variable to 0, but host_cache_size is more flexible because it can also be used to resize, enable, or disable the host cache at runtime, not just at server startup.

    If you start the server with --skip-host-cache, that does not prevent changes to the value of host_cache_size, but such changes have no effect and the cache is not re-enabled even if host_cache_size is set larger than 0.

  • --skip-innodb

    Disable the InnoDB storage engine. In this case, because the default storage engine is InnoDB, the server will not start unless you also use --default-storage-engine and --default-tmp-storage-engine to set the default to some other engine for both permanent and TEMPORARY tables.

    As of MySQL 5.6.21, the --skip-innodb option is deprecated. Its use results in a warning. This option will be removed in a future MySQL release.

  • --skip-name-resolve

    Do not resolve host names when checking client connections. Use only IP addresses. If you use this option, all Host column values in the grant tables must be IP addresses or localhost. See Section 8.11.5.2, “DNS Lookup Optimization and the Host Cache”.

    Depending on the network configuration of your system and the Host values for your accounts, clients may need to connect using an explicit --host option, such as --host=localhost, --host=127.0.0.1, or --host=::1.

  • --skip-networking

    Do not listen for TCP/IP connections at all. All interaction with mysqld must be made using named pipes or shared memory (on Windows) or Unix socket files (on Unix). This option is highly recommended for systems where only local clients are permitted. See Section 8.11.5.2, “DNS Lookup Optimization and the Host Cache”.

  • --skip-partition

    Command-Line Format--skip-partition
     --disable-partition

    Disables user-defined partitioning. Partitioned tables can be seen using SHOW TABLES or by querying the INFORMATION_SCHEMA.TABLES table, but cannot be created or modified, nor can data in such tables be accessed. All partition-specific columns in the INFORMATION_SCHEMA.PARTITIONS table display NULL.

    Since DROP TABLE removes table definition (.frm) files, this statement works on partitioned tables even when partitioning is disabled using the option. The statement, however, does not remove .par files associated with partitioned tables in such cases. For this reason, you should avoid dropping partitioned tables with partitioning disabled, or take action to remove the orphaned .par files manually.

  • --ssl*

    Options that begin with --ssl specify whether to permit clients to connect using SSL and indicate where to find SSL keys and certificates. See Section 6.3.10.4, “SSL Command Options”.

  • --standalone

    Command-Line Format--standalone
    Platform SpecificWindows

    Available on Windows only; instructs the MySQL server not to run as a service.

  • --super-large-pages

    Command-Line Format--super-large-pages
    Platform SpecificSolaris
    Permitted Values (Solaris)Typeboolean
    DefaultFALSE

    Standard use of large pages in MySQL attempts to use the largest size supported, up to 4MB. Under Solaris, a super large pages feature enables uses of pages up to 256MB. This feature is available for recent SPARC platforms. It can be enabled or disabled by using the --super-large-pages or --skip-super-large-pages option.

  • --symbolic-links, --skip-symbolic-links

    Command-Line Format--symbolic-links

    Enable or disable symbolic link support. This option has different effects on Windows and Unix:

  • --skip-show-database

    Command-Line Format--skip-show-database
    System VariableNameskip_show_database
    Variable ScopeGlobal
    Dynamic VariableNo

    This option sets the skip_show_database system variable that controls who is permitted to use the SHOW DATABASES statement. See Section 5.1.4, “Server System Variables”.

  • --skip-stack-trace

    Command-Line Format--skip-stack-trace

    Do not write stack traces. This option is useful when you are running mysqld under a debugger. On some systems, you also must use this option to get a core file. See Section 24.4, “Debugging and Porting MySQL”.

  • --skip-thread-priority

    Deprecated5.1.29
    Removed5.6.1
    Command-Line Format--skip-thread-priority

    Disable using thread priorities for faster response time. This option was unused and was removed in MySQL 5.6.1.

  • --slow-query-log[={0|1}]

    Command-Line Format--slow-query-log
    System VariableNameslow_query_log
    Variable ScopeGlobal
    Dynamic VariableYes
    Permitted ValuesTypeboolean
    DefaultOFF

    Specify the initial slow query log state. With no argument or an argument of 1, the --slow-query-log option enables the log. If omitted or given with an argument of 0, the option disables the log.

  • --slow-start-timeout=timeout

    Introduced5.6.5
    Command-Line Format--slow-start-timeout=#
    Permitted Values (Windows)Typenumeric
    Default15000

    This option controls the Windows service control manager's service start timeout. The value is the maximum number of milliseconds that the service control manager waits before trying to kill the windows service during startup. The default value is 15000 (15 seconds). If the MySQL service takes too long to start, you may need to increase this value. A value of 0 means there is no timeout.

  • --socket=path

    Command-Line Format--socket=file_name
    System VariableNamesocket
    Variable ScopeGlobal
    Dynamic VariableNo
    Permitted ValuesTypefile name
    Default/tmp/mysql.sock

    On Unix, this option specifies the Unix socket file to use when listening for local connections. The default value is /tmp/mysql.sock. If this option is given, the server creates the file in the data directory unless an absolute path name is given to specify a different directory. On Windows, the option specifies the pipe name to use when listening for local connections that use a named pipe. The default value is MySQL (not case sensitive).

  • --sql-mode=value[,value[,value...]]

    Command-Line Format--sql-mode=name
    System VariableNamesql_mode
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Permitted Values (<= 5.6.5)Typeset
    Default''
    Valid ValuesALLOW_INVALID_DATES
    ANSI_QUOTES
    ERROR_FOR_DIVISION_BY_ZERO
    HIGH_NOT_PRECEDENCE
    IGNORE_SPACE
    NO_AUTO_CREATE_USER
    NO_AUTO_VALUE_ON_ZERO
    NO_BACKSLASH_ESCAPES
    NO_DIR_IN_CREATE
    NO_ENGINE_SUBSTITUTION
    NO_FIELD_OPTIONS
    NO_KEY_OPTIONS
    NO_TABLE_OPTIONS
    NO_UNSIGNED_SUBTRACTION
    NO_ZERO_DATE
    NO_ZERO_IN_DATE
    ONLY_FULL_GROUP_BY
    PAD_CHAR_TO_FULL_LENGTH
    PIPES_AS_CONCAT
    REAL_AS_FLOAT
    STRICT_ALL_TABLES
    STRICT_TRANS_TABLES
    Permitted Values (>= 5.6.6)Typeset
    DefaultNO_ENGINE_SUBSTITUTION
    Valid ValuesALLOW_INVALID_DATES
    ANSI_QUOTES
    ERROR_FOR_DIVISION_BY_ZERO
    HIGH_NOT_PRECEDENCE
    IGNORE_SPACE
    NO_AUTO_CREATE_USER
    NO_AUTO_VALUE_ON_ZERO
    NO_BACKSLASH_ESCAPES
    NO_DIR_IN_CREATE
    NO_ENGINE_SUBSTITUTION
    NO_FIELD_OPTIONS
    NO_KEY_OPTIONS
    NO_TABLE_OPTIONS
    NO_UNSIGNED_SUBTRACTION
    NO_ZERO_DATE
    NO_ZERO_IN_DATE
    ONLY_FULL_GROUP_BY
    PAD_CHAR_TO_FULL_LENGTH
    PIPES_AS_CONCAT
    REAL_AS_FLOAT
    STRICT_ALL_TABLES
    STRICT_TRANS_TABLES

    Set the SQL mode. Prior to MySQL 5.6.6, the default was '' (an empty string); beginning with MySQL 5.6.6, the default is NO_ENGINE_SUBSTITUTION. See Section 5.1.7, “Server SQL Modes”.

    Note

    MySQL installation programs may configure the SQL mode during the installation process. For example, mysql_install_db creates a default option file named my.cnf in the base installation directory. This file contains a line that sets the SQL mode; see Section 4.4.3, “mysql_install_db — Initialize MySQL Data Directory”.

    If the SQL mode differs from the default or from what you expect, check for a setting in an option file that the server reads at startup.

  • --sysdate-is-now

    Command-Line Format--sysdate-is-now
    Permitted ValuesTypeboolean
    DefaultFALSE

    SYSDATE() by default returns the time at which it executes, not the time at which the statement in which it occurs begins executing. This differs from the behavior of NOW(). This option causes SYSDATE() to be an alias for NOW(). For information about the implications for binary logging and replication, see the description for SYSDATE() in Section 12.7, “Date and Time Functions” and for SET TIMESTAMP in Section 5.1.4, “Server System Variables”.

  • --tc-heuristic-recover={COMMIT|ROLLBACK}

    Command-Line Format--tc-heuristic-recover=name
    Permitted ValuesTypeenumeration
    DefaultCOMMIT
    Valid ValuesCOMMIT
    ROLLBACK

    The type of decision to use in the heuristic recovery process. Currently, this option is unused.

  • --temp-pool

    Command-Line Format--temp-pool
    Permitted ValuesTypeboolean
    DefaultTRUE

    This option causes most temporary files created by the server to use a small set of names, rather than a unique name for each new file. This works around a problem in the Linux kernel dealing with creating many new files with different names. With the old behavior, Linux seems to leak memory, because it is being allocated to the directory entry cache rather than to the disk cache. This option is ignored except on Linux.

  • --transaction-isolation=level

    Command-Line Format--transaction-isolation=name
    Permitted ValuesTypeenumeration
    DefaultREPEATABLE-READ
    Valid ValuesREAD-UNCOMMITTED
    READ-COMMITTED
    REPEATABLE-READ
    SERIALIZABLE

    Sets the default transaction isolation level. The level value can be READ-UNCOMMITTED, READ-COMMITTED, REPEATABLE-READ, or SERIALIZABLE. See Section 13.3.6, “SET TRANSACTION Syntax”.

    The default transaction isolation level can also be set at runtime using the SET TRANSACTION statement or by setting the tx_isolation system variable.

  • --transaction-read-only

    Introduced5.6.5
    Command-Line Format--transaction-read-only
    Permitted ValuesTypeboolean
    DefaultOFF

    Sets the default transaction access mode. By default, read-only mode is disabled, so the mode is read/write.

    To set the default transaction access mode at runtime, use the SET TRANSACTION statement or set the tx_read_only system variable. See Section 13.3.6, “SET TRANSACTION Syntax”.

    This option was added in MySQL 5.6.5.

  • --tmpdir=path, -t path

    Command-Line Format--tmpdir=path
    System VariableNametmpdir
    Variable ScopeGlobal
    Dynamic VariableNo
    Permitted ValuesTypedirectory name

    The path of the directory to use for creating temporary files. It might be useful if your default /tmp directory resides on a partition that is too small to hold temporary tables. This option accepts several paths that are used in round-robin fashion. Paths should be separated by colon characters (:) on Unix and semicolon characters (;) on Windows. If the MySQL server is acting as a replication slave, you should not set --tmpdir to point to a directory on a memory-based file system or to a directory that is cleared when the server host restarts. For more information about the storage location of temporary files, see Section B.5.4.4, “Where MySQL Stores Temporary Files”. A replication slave needs some of its temporary files to survive a machine restart so that it can replicate temporary tables or LOAD DATA INFILE operations. If files in the temporary file directory are lost when the server restarts, replication fails.

  • --user={user_name|user_id}, -u {user_name|user_id}

    Command-Line Format--user=name
    Permitted ValuesTypestring

    Run the mysqld server as the user having the name user_name or the numeric user ID user_id. (User in this context refers to a system login account, not a MySQL user listed in the grant tables.)

    This option is mandatory when starting mysqld as root. The server changes its user ID during its startup sequence, causing it to run as that particular user rather than as root. See Section 6.1.1, “Security Guidelines”.

    To avoid a possible security hole where a user adds a --user=root option to a my.cnf file (thus causing the server to run as root), mysqld uses only the first --user option specified and produces a warning if there are multiple --user options. Options in /etc/my.cnf and $MYSQL_HOME/my.cnf are processed before command-line options, so it is recommended that you put a --user option in /etc/my.cnf and specify a value other than root. The option in /etc/my.cnf is found before any other --user options, which ensures that the server runs as a user other than root, and that a warning results if any other --user option is found.

  • --verbose, -v

    Use this option with the --help option for detailed help.

  • --version, -V

    Display version information and exit.

You can assign a value to a server system variable by using an option of the form --var_name=value. For example, --key_buffer_size=32M sets the key_buffer_size variable to a value of 32MB.

Note that when you assign a value to a variable, MySQL might automatically correct the value to stay within a given range, or adjust the value to the closest permissible value if only certain values are permitted.

If you want to restrict the maximum value to which a variable can be set at runtime with SET, you can define this by using the --maximum-var_name=value command-line option.

You can change the values of most system variables for a running server with the SET statement. See Section 13.7.4, “SET Syntax”.

Section 5.1.4, “Server System Variables”, provides a full description for all variables, and additional information for setting them at server startup and runtime. Section 8.11.2, “Tuning Server Parameters”, includes information on optimizing the server by tuning system variables.

5.1.4 Server System Variables

The MySQL server maintains many system variables that indicate how it is configured. Each system variable has a default value. System variables can be set at server startup using options on the command line or in an option file. Most of them can be changed dynamically while the server is running by means of the SET statement, which enables you to modify operation of the server without having to stop and restart it. You can refer to system variable values in expressions.

There are several ways to see the names and values of system variables:

  • To see the values that a server will use based on its compiled-in defaults and any option files that it reads, use this command:

    mysqld --verbose --help
    
  • To see the values that a server will use based on its compiled-in defaults, ignoring the settings in any option files, use this command:

    mysqld --no-defaults --verbose --help
    
  • To see the current values used by a running server, use the SHOW VARIABLES statement.

This section provides a description of each system variable. Variables with no version indicated are present in all MySQL 5.6 releases. For historical information concerning their implementation, please see http://dev.mysql.com/doc/refman/5.0/en/, and http://dev.mysql.com/doc/refman/4.1/en/.

The following table lists all available system variables.

Table 5.3 System Variable Summary

NameCmd-LineOption FileSystem VarVar ScopeDynamic
audit_log_buffer_sizeYesYesYesGlobalNo
audit_log_connection_policyYesYesYesGlobalYes
audit_log_current_session  YesBothNo
audit_log_exclude_accountsYesYesYesGlobalYes
audit_log_fileYesYesYesGlobalNo
audit_log_flush  YesGlobalYes
audit_log_formatYesYesYesGlobalNo
audit_log_include_accountsYesYesYesGlobalYes
audit_log_policyYesYesYesGlobalVaries
audit_log_rotate_on_sizeYesYesYesGlobalYes
audit_log_statement_policyYesYesYesGlobalYes
audit_log_strategyYesYesYesGlobalNo
auto_increment_increment  YesBothYes
auto_increment_offset  YesBothYes
autocommitYesYesYesBothYes
automatic_sp_privileges  YesGlobalYes
back_log  YesGlobalNo
basedirYesYesYesGlobalNo
big-tablesYesYes  Yes
- Variable: big_tables  YesBothYes
bind-addressYesYes  No
- Variable: bind_address  YesGlobalNo
binlog_cache_sizeYesYesYesGlobalYes
binlog_checksum  YesGlobalYes
binlog_direct_non_transactional_updatesYesYesYesBothYes
binlog_error_actionYesYesYesBothYes
binlog-formatYesYes  Yes
- Variable: binlog_format  YesBothYes
binlog_gtid_recovery_simplifiedYesYesYesGlobalNo
binlog_max_flush_queue_time  YesGlobalYes
binlog_order_commits  YesGlobalYes
binlog_row_imageYesYesYesBothYes
binlog_rows_query_log_events  YesBothYes
binlog_stmt_cache_sizeYesYesYesGlobalYes
binlogging_impossible_modeYesYesYesBothYes
block_encryption_modeYesYesYesBothYes
bulk_insert_buffer_sizeYesYesYesBothYes
character_set_client  YesBothYes
character_set_connection  YesBothYes
character_set_database[a]  YesBothYes
character-set-filesystemYesYes  Yes
- Variable: character_set_filesystem  YesBothYes
character_set_results  YesBothYes
character-set-serverYesYes  Yes
- Variable: character_set_server  YesBothYes
character_set_system  YesGlobalNo
character-sets-dirYesYes  No
- Variable: character_sets_dir  YesGlobalNo
collation_connection  YesBothYes
collation_database[b]  YesBothYes
collation-serverYesYes  Yes
- Variable: collation_server  YesBothYes
completion_typeYesYesYesBothYes
concurrent_insertYesYesYesGlobalYes
connect_timeoutYesYesYesGlobalYes
core_file  YesGlobalNo
daemon_memcached_enable_binlogYesYesYesGlobalNo
daemon_memcached_engine_lib_nameYesYesYesGlobalNo
daemon_memcached_engine_lib_pathYesYesYesGlobalNo
daemon_memcached_optionYesYesYesGlobalNo
daemon_memcached_r_batch_sizeYesYesYesGlobalNo
daemon_memcached_w_batch_sizeYesYesYesGlobalNo
datadirYesYesYesGlobalNo
date_format  YesGlobalNo
datetime_format  YesGlobalNo
debugYesYesYesBothYes
debug_sync  YesSessionYes
default-storage-engineYesYes  Yes
- Variable: default_storage_engine  YesBothYes
default_tmp_storage_engineYesYesYesBothYes
default_week_formatYesYesYesBothYes
delay-key-writeYesYes  Yes
- Variable: delay_key_write  YesGlobalYes
delayed_insert_limitYesYesYesGlobalYes
delayed_insert_timeoutYesYesYesGlobalYes
delayed_queue_sizeYesYesYesGlobalYes
disable_gtid_unsafe_statementsYesYesYesGlobalNo
disable-gtid-unsafe-statementsYesYesYesGlobalNo
disconnect_on_expired_passwordYesYesYesSessionNo
div_precision_incrementYesYesYesBothYes
end_markers_in_json  YesBothYes
enforce_gtid_consistencyYesYesYesGlobalNo
enforce-gtid-consistencyYesYesYesGlobalNo
engine-condition-pushdownYesYes  Yes
- Variable: engine_condition_pushdown  YesBothYes
eq_range_index_dive_limit  YesBothYes
error_count  YesSessionNo
event-schedulerYesYes  Yes
- Variable: event_scheduler  YesGlobalYes
expire_logs_daysYesYesYesGlobalYes
explicit_defaults_for_timestampYesYesYesSessionNo
external_user  YesSessionNo
flushYesYesYesGlobalYes
flush_timeYesYesYesGlobalYes
foreign_key_checks  YesBothYes
ft_boolean_syntaxYesYesYesGlobalYes
ft_max_word_lenYesYesYesGlobalNo
ft_min_word_lenYesYesYesGlobalNo
ft_query_expansion_limitYesYesYesGlobalNo
ft_stopword_fileYesYesYesGlobalNo
general-logYesYes  Yes
- Variable: general_log  YesGlobalYes
general_log_fileYesYesYesGlobalYes
group_concat_max_lenYesYesYesBothYes
gtid_done  YesBothNo
gtid_executed  YesBothNo
gtid_lost  YesGlobalNo
gtid_mode  YesGlobalNo
gtid-modeYesYes  No
- Variable: gtid_mode  YesGlobalNo
gtid_next  YesSessionYes
gtid_owned  YesBothNo
gtid_purged  YesGlobalYes
have_compress  YesGlobalNo
have_crypt  YesGlobalNo
have_csv  YesGlobalNo
have_dynamic_loading  YesGlobalNo
have_geometry  YesGlobalNo
have_innodb  YesGlobalNo
have_ndbcluster  YesGlobalNo
have_openssl  YesGlobalNo
have_partitioning  YesGlobalNo
have_profiling  YesGlobalNo
have_query_cache  YesGlobalNo
have_rtree_keys  YesGlobalNo
have_ssl  YesGlobalNo
have_symlink  YesGlobalNo
host_cache_size  YesGlobalYes
hostname  YesGlobalNo
identity  YesSessionYes
ignore-builtin-innodbYesYes  No
- Variable: ignore_builtin_innodb  YesGlobalNo
ignore_db_dirs  YesGlobalNo
init_connectYesYesYesGlobalYes
init-fileYesYes  No
- Variable: init_file  YesGlobalNo
init_slaveYesYesYesGlobalYes
innodb_adaptive_flushingYesYesYesGlobalYes
innodb_adaptive_flushing_lwmYesYesYesGlobalYes
innodb_adaptive_hash_indexYesYesYesGlobalYes
innodb_adaptive_max_sleep_delayYesYesYesGlobalYes
innodb_additional_mem_pool_sizeYesYesYesGlobalNo
innodb_api_bk_commit_intervalYesYesYesGlobalYes
innodb_api_disable_rowlockYesYesYesGlobalNo
innodb_api_enable_binlogYesYesYesGlobalNo
innodb_api_enable_mdlYesYesYesGlobalNo
innodb_api_trx_levelYesYesYesGlobalYes
innodb_autoextend_incrementYesYesYesGlobalYes
innodb_autoinc_lock_modeYesYesYesGlobalNo
innodb_buffer_pool_dump_at_shutdownYesYesYesGlobalYes
innodb_buffer_pool_dump_nowYesYesYesGlobalYes
innodb_buffer_pool_filenameYesYesYesGlobalYes
innodb_buffer_pool_instancesYesYesYesGlobalNo
innodb_buffer_pool_load_abortYesYesYesGlobalYes
innodb_buffer_pool_load_at_startupYesYesYesGlobalNo
innodb_buffer_pool_load_nowYesYesYesGlobalYes
innodb_buffer_pool_sizeYesYesYesGlobalNo
innodb_change_buffer_max_sizeYesYesYesGlobalYes
innodb_change_bufferingYesYesYesGlobalYes
innodb_checksum_algorithmYesYesYesGlobalYes
innodb_checksumsYesYesYesGlobalNo
innodb_cmp_per_index_enabledYesYesYesGlobalYes
innodb_commit_concurrencyYesYesYesGlobalYes
innodb_compression_failure_threshold_pctYesYesYesGlobalYes
innodb_compression_levelYesYesYesGlobalYes
innodb_compression_pad_pct_maxYesYesYesGlobalYes
innodb_concurrency_ticketsYesYesYesGlobalYes
innodb_data_file_pathYesYesYesGlobalNo
innodb_data_home_dirYesYesYesGlobalNo
innodb_disable_sort_file_cacheYesYesYesGlobalYes
innodb_doublewriteYesYesYesGlobalNo
innodb_fast_shutdownYesYesYesGlobalYes
innodb_file_formatYesYesYesGlobalYes
innodb_file_format_checkYesYesYesGlobalNo
innodb_file_format_maxYesYesYesGlobalYes
innodb_file_per_tableYesYesYesGlobalYes
innodb_flush_log_at_timeout  YesGlobalYes
innodb_flush_log_at_trx_commitYesYesYesGlobalYes
innodb_flush_methodYesYesYesGlobalNo
innodb_flush_neighborsYesYesYesGlobalYes
innodb_flushing_avg_loopsYesYesYesGlobalYes
innodb_force_load_corruptedYesYesYesGlobalNo
innodb_force_recoveryYesYesYesGlobalNo
innodb_ft_aux_table  YesGlobalYes
innodb_ft_cache_sizeYesYesYesGlobalNo
innodb_ft_enable_diag_printYesYesYesGlobalYes
innodb_ft_enable_stopwordYesYesYesGlobalYes
innodb_ft_max_token_sizeYesYesYesGlobalNo
innodb_ft_min_token_sizeYesYesYesGlobalNo
innodb_ft_num_word_optimizeYesYesYesGlobalYes
innodb_ft_result_cache_limitYesYesYesGlobalYes
innodb_ft_server_stopword_tableYesYesYesGlobalYes
innodb_ft_sort_pll_degreeYesYesYesGlobalNo
innodb_ft_total_cache_sizeYesYesYesGlobalNo
innodb_ft_user_stopword_tableYesYesYesBothYes
innodb_io_capacityYesYesYesGlobalYes
innodb_io_capacity_maxYesYesYesGlobalYes
innodb_large_prefixYesYesYesGlobalYes
innodb_lock_wait_timeoutYesYesYesBothYes
innodb_locks_unsafe_for_binlogYesYesYesGlobalNo
innodb_log_buffer_sizeYesYesYesGlobalNo
innodb_log_compressed_pagesYesYesYesGlobalYes
innodb_log_file_sizeYesYesYesGlobalNo
innodb_log_files_in_groupYesYesYesGlobalNo
innodb_log_group_home_dirYesYesYesGlobalNo
innodb_lru_scan_depthYesYesYesGlobalYes
innodb_max_dirty_pages_pctYesYesYesGlobalYes
innodb_max_dirty_pages_pct_lwmYesYesYesGlobalYes
innodb_max_purge_lagYesYesYesGlobalYes
innodb_max_purge_lag_delayYesYesYesGlobalYes
innodb_mirrored_log_groupsYesYesYesGlobalNo
innodb_monitor_disableYesYesYesGlobalYes
innodb_monitor_enableYesYesYesGlobalYes
innodb_monitor_resetYesYesYesGlobalYes
innodb_monitor_reset_allYesYesYesGlobalYes
innodb_old_blocks_pctYesYesYesGlobalYes
innodb_old_blocks_timeYesYesYesGlobalYes
innodb_online_alter_log_max_sizeYesYesYesGlobalYes
innodb_open_filesYesYesYesGlobalNo
innodb_optimize_fulltext_onlyYesYesYesGlobalYes
innodb_page_sizeYesYesYesGlobalNo
innodb_print_all_deadlocksYesYesYesGlobalYes
innodb_purge_batch_sizeYesYesYesGlobalYes
innodb_purge_threadsYesYesYesGlobalNo
innodb_random_read_aheadYesYesYesGlobalYes
innodb_read_ahead_thresholdYesYesYesGlobalYes
innodb_read_io_threadsYesYesYesGlobalNo
innodb_read_onlyYesYesYesGlobalNo
innodb_replication_delayYesYesYesGlobalYes
innodb_rollback_on_timeoutYesYesYesGlobalNo
innodb_rollback_segmentsYesYesYesGlobalYes
innodb_sort_buffer_sizeYesYesYesGlobalNo
innodb_spin_wait_delayYesYesYesGlobalYes
innodb_stats_auto_recalcYesYesYesGlobalYes
innodb_stats_methodYesYesYesGlobalYes
innodb_stats_on_metadataYesYesYesGlobalYes
innodb_stats_persistentYesYesYesGlobalYes
innodb_stats_persistent_sample_pagesYesYesYesGlobalYes
innodb_stats_sample_pagesYesYesYesGlobalYes
innodb_stats_transient_sample_pagesYesYesYesGlobalYes
innodb_status_outputYesYesYesGlobalYes
innodb_status_output_locksYesYesYesGlobalYes
innodb_strict_modeYesYesYesBothYes
innodb_support_xaYesYesYesBothYes
innodb_sync_array_sizeYesYesYesGlobalNo
innodb_sync_spin_loopsYesYesYesGlobalYes
innodb_table_locksYesYesYesBothYes
innodb_thread_concurrencyYesYesYesGlobalYes
innodb_thread_sleep_delayYesYesYesGlobalYes
innodb_undo_directoryYesYesYesGlobalNo
innodb_undo_logsYesYesYesGlobalYes
innodb_undo_tablespacesYesYesYesGlobalNo
innodb_use_native_aioYesYesYesGlobalNo
innodb_use_sys_mallocYesYesYesGlobalNo
innodb_version  YesGlobalNo
innodb_write_io_threadsYesYesYesGlobalNo
insert_id  YesSessionYes
interactive_timeoutYesYesYesBothYes
join_buffer_sizeYesYesYesBothYes
keep_files_on_createYesYesYesBothYes
key_buffer_sizeYesYesYesGlobalYes
key_cache_age_thresholdYesYesYesGlobalYes
key_cache_block_sizeYesYesYesGlobalYes
key_cache_division_limitYesYesYesGlobalYes
languageYesYesYesGlobalNo
large_files_support  YesGlobalNo
large_page_size  YesGlobalNo
large-pagesYesYes  No
- Variable: large_pages  YesGlobalNo
last_insert_id  YesSessionYes
lc-messagesYesYes  Yes
- Variable: lc_messages  YesBothYes
lc-messages-dirYesYes  No
- Variable: lc_messages_dir  YesGlobalNo
lc_time_names  YesBothYes
license  YesGlobalNo
local_infile  YesGlobalYes
lock_wait_timeoutYesYesYesBothYes
locked_in_memory  YesGlobalNo
logYesYesYesGlobalYes
log_bin  YesGlobalNo
log-binYesYesYesGlobalNo
log_bin_basename  YesGlobalNo
log_bin_index  YesGlobalNo
log-bin-trust-function-creatorsYesYes  Yes
- Variable: log_bin_trust_function_creators  YesGlobalYes
log_bin_use_v1_row_eventsYesYesYesGlobalNo
log-bin-use-v1-row-eventsYesYes  No
- Variable: log_bin_use_v1_row_events  YesGlobalNo
log-errorYesYes  No
- Variable: log_error  YesGlobalNo
log-outputYesYes  Yes
- Variable: log_output  YesGlobalYes
log-queries-not-using-indexesYesYes  Yes
- Variable: log_queries_not_using_indexes  YesGlobalYes
log-slave-updatesYesYes  No
- Variable: log_slave_updates  YesGlobalNo
log_slave_updatesYesYesYesGlobalNo
log_slow_admin_statements  YesGlobalYes
log-slow-queriesYesYes  Yes
- Variable: log_slow_queries  YesGlobalYes
log_slow_slave_statements  YesGlobalYes
log_throttle_queries_not_using_indexes  YesGlobalYes
log-warningsYesYes  Yes
- Variable: log_warnings  YesVariesYes
long_query_timeYesYesYesBothYes
low-priority-updatesYesYes  Yes
- Variable: low_priority_updates  YesBothYes
lower_case_file_system  YesGlobalNo
lower_case_table_namesYesYesYesGlobalNo
master_info_repositoryYesYesYesGlobalYes
master_verify_checksum  YesGlobalYes
max_allowed_packetYesYesYesGlobalYes
max_binlog_cache_sizeYesYesYesGlobalYes
max_binlog_sizeYesYesYesGlobalYes
max_binlog_stmt_cache_sizeYesYesYesGlobalYes
max_connect_errorsYesYesYesGlobalYes
max_connectionsYesYesYesGlobalYes
max_delayed_threadsYesYesYesBothYes
max_error_countYesYesYesBothYes
max_heap_table_sizeYesYesYesBothYes
max_insert_delayed_threads  YesBothYes
max_join_sizeYesYesYesBothYes
max_length_for_sort_dataYesYesYesBothYes
max_prepared_stmt_countYesYesYesGlobalYes
max_relay_log_sizeYesYesYesGlobalYes
max_seeks_for_keyYesYesYesBothYes
max_sort_lengthYesYesYesBothYes
max_sp_recursion_depthYesYesYesBothYes
max_user_connectionsYesYesYesBothYes
max_write_lock_countYesYesYesGlobalYes
metadata_locks_cache_size  YesGlobalNo
metadata_locks_hash_instances  YesGlobalNo
min-examined-row-limitYesYesYesBothYes
myisam_data_pointer_sizeYesYesYesGlobalYes
myisam_max_sort_file_sizeYesYesYesGlobalYes
myisam_mmap_sizeYesYesYesGlobalNo
myisam_recover_options  YesGlobalNo
myisam_repair_threadsYesYesYesBothYes
myisam_sort_buffer_sizeYesYesYesBothYes
myisam_stats_methodYesYesYesBothYes
myisam_use_mmapYesYesYesGlobalYes
named_pipe  YesGlobalNo
ndb_autoincrement_prefetch_szYesYesYesBothYes
ndb-batch-sizeYesYesYesGlobalNo
ndb-blob-read-batch-bytesYesYesYesBothYes
ndb-blob-write-batch-bytesYesYesYesBothYes
ndb_cache_check_timeYesYesYesGlobalYes
ndb-cluster-connection-poolYesYesYesGlobalNo
ndb-deferred-constraintsYesYes  Yes
- Variable: ndb_deferred_constraints  YesBothYes
ndb_deferred_constraintsYesYesYesBothYes
ndb_distributionYesYesYesGlobalYes
ndb-distributionYesYes  Yes
- Variable: ndb_distribution  YesGlobalYes
ndb_eventbuffer_free_percentYesYesYesGlobalYes
ndb_eventbuffer_max_allocYesYesYesGlobalYes
ndb_extra_loggingYesYesYesGlobalYes
ndb_force_sendYesYesYesBothYes
ndb_index_stat_cache_entriesYesYesYesBothYes
ndb_index_stat_enableYesYesYesBothYes
ndb_index_stat_optionYesYesYesBothYes
ndb_index_stat_update_freqYesYesYesBothYes
ndb_join_pushdown  YesBothYes
ndb-log-apply-statusYesYes  No
- Variable: ndb_log_apply_status  YesGlobalNo
ndb_log_apply_statusYesYesYesGlobalNo
ndb_log_binYes YesBothYes
ndb_log_binlog_indexYes YesGlobalYes
ndb_log_empty_epochsYesYesYesGlobalYes
ndb-log-empty-epochsYesYesYesGlobalYes
ndb-log-exclusive-readsYesYes  Yes
- Variable: ndb_log_exclusive_reads  YesBothYes
ndb_log_exclusive_readsYesYesYesBothYes
ndb-log-origYesYes  No
- Variable: ndb_log_orig  YesGlobalNo
ndb_log_origYesYesYesGlobalNo
ndb-log-transaction-idYesYes  No
- Variable: ndb_log_transaction_id  YesGlobalNo
ndb_log_transaction_id  YesGlobalNo
ndb-log-update-as-writeYesYesYesGlobalYes
ndb_log_updated_onlyYesYesYesGlobalYes
ndb_optimization_delay  YesGlobalYes
ndb_optimized_node_selectionYesYesYesGlobalNo
ndb_recv_thread_cpu_mask  YesGlobalYes
ndb_show_foreign_key_mock_tablesYesYesYesGlobalYes
ndb_slave_conflict_roleYesYesYesGlobalYes
Ndb_slave_last_conflict_epoch  YesGlobalNo
Ndb_slave_max_replicated_epoch  YesGlobalNo
ndb_table_no_logging  YesSessionYes
ndb_table_temporary  YesSessionYes
ndb_use_copying_alter_table  YesBothNo
ndb_use_exact_count  YesBothYes
ndb_use_transactionsYesYesYesBothYes
ndb_version  YesGlobalNo
ndb_version_string  YesGlobalNo
ndb-wait-connectedYesYesYesGlobalNo
ndb-wait-setupYesYesYesGlobalNo
ndbinfo_database  YesGlobalNo
ndbinfo_max_bytesYes YesBothYes
ndbinfo_max_rowsYes YesBothYes
ndbinfo_offline  YesGlobalYes
ndbinfo_show_hiddenYes YesBothYes
ndbinfo_table_prefixYes YesBothYes
ndbinfo_version  YesGlobalNo
net_buffer_lengthYesYesYesBothYes
net_read_timeoutYesYesYesBothYes
net_retry_countYesYesYesBothYes
net_write_timeoutYesYesYesBothYes
newYesYesYesBothYes
oldYesYesYesGlobalNo
old-alter-tableYesYes  Yes
- Variable: old_alter_table  YesBothYes
old_passwords  YesBothYes
open-files-limitYesYes  No
- Variable: open_files_limit  YesGlobalNo
optimizer_join_cache_levelYesYesYesBothYes
optimizer_prune_levelYesYesYesBothYes
optimizer_search_depthYesYesYesBothYes
optimizer_switchYesYesYesBothYes
optimizer_trace  YesBothYes
optimizer_trace_features  YesBothYes
optimizer_trace_limit  YesBothYes
optimizer_trace_max_mem_size  YesBothYes
optimizer_trace_offset  YesBothYes
performance_schemaYesYesYesGlobalNo
performance_schema_accounts_sizeYesYesYesGlobalNo
performance_schema_digests_sizeYesYesYesGlobalNo
performance_schema_events_stages_history_long_sizeYesYesYesGlobalNo
performance_schema_events_stages_history_sizeYesYesYesGlobalNo
performance_schema_events_statements_history_long_sizeYesYesYesGlobalNo
performance_schema_events_statements_history_sizeYesYesYesGlobalNo
performance_schema_events_waits_history_long_sizeYesYesYesGlobalNo
performance_schema_events_waits_history_sizeYesYesYesGlobalNo
performance_schema_hosts_sizeYesYesYesGlobalNo
performance_schema_max_cond_classesYesYesYesGlobalNo
performance_schema_max_cond_instancesYesYesYesGlobalNo
performance_schema_max_file_classesYesYesYesGlobalNo
performance_schema_max_file_handlesYesYesYesGlobalNo
performance_schema_max_file_instancesYesYesYesGlobalNo
performance_schema_max_mutex_classesYesYesYesGlobalNo
performance_schema_max_mutex_instancesYesYesYesGlobalNo
performance_schema_max_rwlock_classesYesYesYesGlobalNo
performance_schema_max_rwlock_instancesYesYesYesGlobalNo
performance_schema_max_socket_classesYesYesYesGlobalNo
performance_schema_max_socket_instancesYesYesYesGlobalNo
performance_schema_max_stage_classesYesYesYesGlobalNo
performance_schema_max_statement_classesYesYesYesGlobalNo
performance_schema_max_table_handlesYesYesYesGlobalNo
performance_schema_max_table_instancesYesYesYesGlobalNo
performance_schema_max_thread_classesYesYesYesGlobalNo
performance_schema_max_thread_instancesYesYesYesGlobalNo
performance_schema_session_connect_attrs_sizeYesYesYesGlobalNo
performance_schema_setup_actors_sizeYesYesYesGlobalNo
performance_schema_setup_objects_sizeYesYesYesGlobalNo
performance_schema_users_sizeYesYesYesGlobalNo
pid-fileYesYes  No
- Variable: pid_file  YesGlobalNo
plugin_dirYesYesYesGlobalNo
portYesYesYesGlobalNo
preload_buffer_sizeYesYesYesBothYes
profiling  YesBothYes
profiling_history_sizeYesYesYesBothYes
protocol_version  YesGlobalNo
proxy_user  YesSessionNo
pseudo_slave_mode  YesSessionYes
pseudo_thread_id  YesSessionYes
query_alloc_block_sizeYesYesYesBothYes
query_cache_limitYesYesYesGlobalYes
query_cache_min_res_unitYesYesYesGlobalYes
query_cache_sizeYesYesYesGlobalYes
query_cache_typeYesYesYesBothYes
query_cache_wlock_invalidateYesYesYesBothYes
query_prealloc_sizeYesYesYesBothYes
rand_seed1  YesSessionYes
rand_seed2  YesSessionYes
range_alloc_block_sizeYesYesYesBothYes
read_buffer_sizeYesYesYesBothYes
read_onlyYesYesYesGlobalYes
read_rnd_buffer_sizeYesYesYesBothYes
relay-logYesYes  No
- Variable: relay_log  YesGlobalNo
relay_log_basename  YesGlobalNo
relay-log-indexYesYes  No
- Variable: relay_log_index  YesGlobalNo
relay_log_indexYesYesYesGlobalNo
relay_log_info_fileYesYesYesGlobalNo
relay_log_info_repository  YesGlobalYes
relay_log_purgeYesYesYesGlobalYes
relay_log_recoveryYesYesYesGlobalVaries
relay_log_space_limitYesYesYesGlobalNo
report-hostYesYes  No
- Variable: report_host  YesGlobalNo
report-passwordYesYes  No
- Variable: report_password  YesGlobalNo
report-portYesYes  No
- Variable: report_port  YesGlobalNo
report-userYesYes  No
- Variable: report_user  YesGlobalNo
rpl_semi_sync_master_enabled  YesGlobalYes
rpl_semi_sync_master_timeout  YesGlobalYes
rpl_semi_sync_master_trace_level  YesGlobalYes
rpl_semi_sync_master_wait_no_slave  YesGlobalYes
rpl_semi_sync_slave_enabled  YesGlobalYes
rpl_semi_sync_slave_trace_level  YesGlobalYes
rpl_stop_slave_timeoutYesYesYesGlobalYes
secure-authYesYes  Yes
- Variable: secure_auth  YesGlobalYes
secure-file-privYesYes  No
- Variable: secure_file_priv  YesGlobalNo
server-idYesYes  Yes
- Variable: server_id  YesGlobalYes
server_id_bitsYesYesYesGlobalNo
server-id-bitsYesYes  No
- Variable: server_id_bits  YesGlobalNo
server_uuid  YesGlobalNo
sha256_password_private_key_path  YesGlobalNo
sha256_password_public_key_path  YesGlobalNo
shared_memoryYesYesYesGlobalNo
shared_memory_base_name  YesGlobalNo
simplified_binlog_gtid_recoveryYesYesYesGlobalNo
skip_external_lockingYesYesYesGlobalNo
skip-name-resolveYesYes  No
- Variable: skip_name_resolve  YesGlobalNo
skip-networkingYesYes  No
- Variable: skip_networking  YesGlobalNo
skip-show-databaseYesYes  No
- Variable: skip_show_database  YesGlobalNo
slave_allow_batchingYesYesYesGlobalYes
slave_checkpoint_groupYesYesYesGlobalYes
slave_checkpoint_periodYesYesYesGlobalYes
slave_compressed_protocolYesYesYesGlobalYes
slave_exec_modeYesYesYesGlobalYes
slave-load-tmpdirYesYes  No
- Variable: slave_load_tmpdir  YesGlobalNo
slave_max_allowed_packet  YesGlobalYes
slave-net-timeoutYesYes  Yes
- Variable: slave_net_timeout  YesGlobalYes
slave_parallel_workersYes YesGlobalYes
slave_pending_jobs_size_max  YesGlobalYes
slave_rows_search_algorithms  YesGlobalYes
slave-skip-errorsYesYes  No
- Variable: slave_skip_errors  YesGlobalNo
slave_sql_verify_checksum  YesGlobalYes
slave_transaction_retriesYesYesYesGlobalYes
slave_type_conversionsYesYesYesGlobalNo
slow_launch_timeYesYesYesGlobalYes
slow-query-logYesYes  Yes
- Variable: slow_query_log  YesGlobalYes
slow_query_log_fileYesYesYesGlobalYes
socketYesYesYesGlobalNo
sort_buffer_sizeYesYesYesBothYes
sql_auto_is_null  YesBothYes
sql_big_selects  YesBothYes
sql_big_tables  YesBothYes
sql_buffer_result  YesBothYes
sql_log_bin  YesBothYes
sql_log_off  YesBothYes
sql_low_priority_updates  YesBothYes
sql_max_join_size  YesBothYes
sql-modeYesYes  Yes
- Variable: sql_mode  YesBothYes
sql_notes  YesBothYes
sql_quote_show_create  YesBothYes
sql_safe_updates  YesBothYes
sql_select_limit  YesBothYes
sql_slave_skip_counter  YesGlobalYes
sql_warnings  YesBothYes
ssl-caYesYes  No
- Variable: ssl_ca  YesGlobalNo
ssl-capathYesYes  No
- Variable: ssl_capath  YesGlobalNo
ssl-certYesYes  No
- Variable: ssl_cert  YesGlobalNo
ssl-cipherYesYes  No
- Variable: ssl_cipher  YesGlobalNo
ssl-crlYesYes  No
- Variable: ssl_crl  YesGlobalNo
ssl-crlpathYesYes  No
- Variable: ssl_crlpath  YesGlobalNo
ssl-keyYesYes  No
- Variable: ssl_key  YesGlobalNo
storage_engine  YesBothYes
stored_program_cacheYesYesYesGlobalYes
sync_binlogYesYesYesGlobalYes
sync_frmYesYesYesGlobalYes
sync_master_infoYesYesYesGlobalYes
sync_relay_logYesYesYesGlobalYes
sync_relay_log_infoYesYesYesGlobalYes
system_time_zone  YesGlobalNo
table_definition_cache  YesGlobalYes
table_open_cache  YesGlobalYes
table_open_cache_instances  YesGlobalNo
thread_cache_sizeYesYesYesGlobalYes
thread_concurrencyYesYesYesGlobalNo
thread_handlingYesYesYesGlobalNo
thread_pool_algorithmYesYesYesGlobalNo
thread_pool_high_priority_connectionYesYesYesBothYes
thread_pool_max_unused_threadsYesYesYesGlobalYes
thread_pool_prio_kickup_timerYesYesYesBothYes
thread_pool_sizeYesYesYesGlobalNo
thread_pool_stall_limitYesYesYesGlobalYes
thread_stackYesYesYesGlobalNo
time_format  YesGlobalNo
time_zone  YesBothYes
timed_mutexesYesYesYesGlobalYes
timestamp  YesSessionYes
tmp_table_sizeYesYesYesBothYes
tmpdirYesYesYesGlobalNo
transaction_alloc_block_sizeYesYesYesBothYes
transaction_allow_batching  YesSessionYes
transaction_prealloc_sizeYesYesYesBothYes
tx_isolation  YesBothYes
tx_read_only  YesBothYes
unique_checks  YesBothYes
updatable_views_with_limitYesYesYesBothYes
validate_password_dictionary_file  YesGlobalNo
validate_password_length  YesGlobalYes
validate_password_mixed_case_count  YesGlobalYes
validate_password_number_count  YesGlobalYes
validate_password_policy  YesGlobalYes
validate_password_special_char_count  YesGlobalYes
validate_user_plugins  YesGlobalNo
version  YesGlobalNo
version_comment  YesGlobalNo
version_compile_machine  YesGlobalNo
version_compile_os  YesGlobalNo
wait_timeoutYesYesYesBothYes
warning_count  YesSessionNo

[a] This option is dynamic, but only the server should set this information. You should not set the value of this variable manually.

[b] This option is dynamic, but only the server should set this information. You should not set the value of this variable manually.


For additional system variable information, see these sections:

Note

Some of the following variable descriptions refer to enabling or disabling a variable. These variables can be enabled with the SET statement by setting them to ON or 1, or disabled by setting them to OFF or 0. However, before MySQL 5.6.2, to set such a variable on the command line or in an option file, you must set it to 1 or 0; setting it to ON or OFF will not work. For example, on the command line, --delay_key_write=1 works but --delay_key_write=ON does not. As of MySQL 5.6.2, boolean variables can be set at startup to the values ON, TRUE, OFF, and FALSE (not case sensitive). See Section 4.2.5, “Program Option Modifiers”.

Some system variables control the size of buffers or caches. For a given buffer, the server might need to allocate internal data structures. These structures typically are allocated from the total memory allocated to the buffer, and the amount of space required might be platform dependent. This means that when you assign a value to a system variable that controls a buffer size, the amount of space actually available might differ from the value assigned. In some cases, the amount might be less than the value assigned. It is also possible that the server will adjust a value upward. For example, if you assign a value of 0 to a variable for which the minimal value is 1024, the server will set the value to 1024.

Values for buffer sizes, lengths, and stack sizes are given in bytes unless otherwise specified.

Some system variables take file name values. Unless otherwise specified, the default file location is the data directory if the value is a relative path name. To specify the location explicitly, use an absolute path name. Suppose that the data directory is /var/mysql/data. If a file-valued variable is given as a relative path name, it will be located under /var/mysql/data. If the value is an absolute path name, its location is as given by the path name.

  • authentication_windows_log_level

    Introduced5.6.10
    Command-Line Format--authentication_windows_log_level
    Permitted ValuesTypenumeric
    Default0
    Min Value0
    Max Value4

    This variable is available only if the authentication_windows Windows authentication plugin is enabled and debugging code is enabled. See Section 6.3.8.6, “The Windows Native Authentication Plugin”.

    This variable sets the logging level for the Windows authentication plugin. The following table shows the permitted values.

    ValueDescription
    0No logging
    1Log only error messages
    2Log level 1 messages and warning messages
    3Log level 2 messages and information notes
    4Log level 3 messages and debug messages

    This variable was added in MySQL 5.6.10.

  • authentication_windows_use_principal_name

    Introduced5.6.10
    Command-Line Format--authentication_windows_use_principal_name
    Permitted ValuesTypeboolean
    DefaultON

    This variable is available only if the authentication_windows Windows authentication plugin is enabled. See Section 6.3.8.6, “The Windows Native Authentication Plugin”.

    A client that authenticates using the InitSecurityContext() function should provide a string identifying the service to which it connects (targetName). MySQL uses the principal name (UPN) of the account under which the server is running. The UPN has the form user_id@computer_name and need not be registered anywhere to be used. This UPN is sent by the server at the beginning of authentication handshake.

    This variable controls whether the server sends the UPN in the initial challenge. By default, the variable is enabled. For security reasons, it can be disabled to avoid sending the server's account name to a client in clear text. If the variable is disabled, the server always sends a 0x00 byte in the first challenge, the client does not specify targetName, and as a result, NTLM authentication is used.

    If the server fails to obtain its UPN (which will happen primarily in environments that do not support Kerberos authentication), the UPN is not sent by the server and NTLM authentication is used.

    This variable was added in MySQL 5.6.10.

  • autocommit

    Command-Line Format--autocommit[=#]
    System VariableNameautocommit
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Permitted ValuesTypeboolean
    DefaultON

    The autocommit mode. If set to 1, all changes to a table take effect immediately. If set to 0, you must use COMMIT to accept a transaction or ROLLBACK to cancel it. If autocommit is 0 and you change it to 1, MySQL performs an automatic COMMIT of any open transaction. Another way to begin a transaction is to use a START TRANSACTION or BEGIN statement. See Section 13.3.1, “START TRANSACTION, COMMIT, and ROLLBACK Syntax”.

    By default, client connections begin with autocommit set to 1. To cause clients to begin with a default of 0, set the global autocommit value by starting the server with the --autocommit=0 option. To set the variable using an option file, include these lines:

    [mysqld]
    autocommit=0
    
  • automatic_sp_privileges

    System VariableNameautomatic_sp_privileges
    Variable ScopeGlobal
    Dynamic VariableYes
    Permitted ValuesTypeboolean
    DefaultTRUE

    When this variable has a value of 1 (the default), the server automatically grants the EXECUTE and ALTER ROUTINE privileges to the creator of a stored routine, if the user cannot already execute and alter or drop the routine. (The ALTER ROUTINE privilege is required to drop the routine.) The server also automatically drops those privileges from the creator when the routine is dropped. If automatic_sp_privileges is 0, the server does not automatically add or drop these privileges.

    The creator of a routine is the account used to execute the CREATE statement for it. This might not be the same as the account named as the DEFINER in the routine definition.

    See also Section 20.2.2, “Stored Routines and MySQL Privileges”.

  • back_log

    System VariableNameback_log
    Variable ScopeGlobal
    Dynamic VariableNo
    Permitted Values (<= 5.6.5)Typenumeric
    Default50
    Min Value1
    Max Value65535
    Permitted Values (>= 5.6.6)Typenumeric
    Default-1 (autosized)
    Min Value1
    Max Value65535

    The number of outstanding connection requests MySQL can have. This comes into play when the main MySQL thread gets very many connection requests in a very short time. It then takes some time (although very little) for the main thread to check the connection and start a new thread. The back_log value indicates how many requests can be stacked during this short time before MySQL momentarily stops answering new requests. You need to increase this only if you expect a large number of connections in a short period of time.

    In other words, this value is the size of the listen queue for incoming TCP/IP connections. Your operating system has its own limit on the size of this queue. The manual page for the Unix listen() system call should have more details. Check your OS documentation for the maximum value for this variable. back_log cannot be set higher than your operating system limit.

    As of MySQL 5.6.6, the default value is based on the following formula, capped to a limit of 900:

    50 + (max_connections / 5)
    

    Before 5.6.6, the default is 50.

  • basedir

    Command-Line Format--basedir=path
    System VariableNamebasedir
    Variable ScopeGlobal
    Dynamic VariableNo
    Permitted ValuesTypedirectory name

    The MySQL installation base directory. This variable can be set with the --basedir option. Relative path names for other variables usually are resolved relative to the base directory.

  • big_tables

    Command-Line Format--big-tables
    System VariableNamebig_tables
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Permitted ValuesTypeboolean
    DefaultOFF

    If set to 1, all temporary tables are stored on disk rather than in memory. This is a little slower, but the error The table tbl_name is full does not occur for SELECT operations that require a large temporary table. The default value for a new connection is 0 (use in-memory temporary tables). Normally, you should never need to set this variable, because in-memory tables are automatically converted to disk-based tables as required.

  • bind_address

    Command-Line Format--bind-address=addr
    System Variable (>= 5.6.1)Namebind_address
    Variable ScopeGlobal
    Dynamic VariableNo
    Permitted Values (<= 5.6.5)Typestring
    Default0.0.0.0
    Permitted Values (>= 5.6.6)Typestring
    Default*

    The value of the --bind-address option. This variable was added in MySQL 5.6.1.

  • block_encryption_mode

    Introduced5.6.17
    Command-Line Format--block_encryption_mode=#
    System VariableNameblock_encryption_mode
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Permitted ValuesTypestring
    Defaultaes-128-ecb

    This variable controls the block encryption mode for block-based algorithms such as AES. It affects encryption for AES_ENCRYPT() and AES_DECRYPT().

    block_encryption_mode takes a value in aes-keylen-mode format, where keylen is the key length in bits and mode is the encryption mode. The value is not case sensitive. Permitted keylen values are 128, 192, and 256. Permitted encryption modes depend on whether MySQL was built using OpenSSL or yaSSL:

    • For OpenSSL, permitted mode values are: ECB, CBC, CFB1, CFB8, CFB128, OFB

    • For yaSSL, permitted mode values are: ECB, CBC

    For example, this statement causes the AES encryption functions to use a key length of 256 bits and the CBC mode:

    SET block_encryption_mode = 'aes-256-cbc';
    

    An error occurs for attempts to set block_encryption_mode to a value containing an unsupported key length or a mode that the SSL library does not support.

    This variable was added in MySQL 5.6.17.

  • bulk_insert_buffer_size

    Command-Line Format--bulk_insert_buffer_size=#
    System VariableNamebulk_insert_buffer_size
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Permitted Values (32-bit platforms)Typenumeric
    Default8388608
    Min Value0
    Max Value4294967295
    Permitted Values (64-bit platforms)Typenumeric
    Default8388608
    Min Value0
    Max Value18446744073709551615

    MyISAM uses a special tree-like cache to make bulk inserts faster for INSERT ... SELECT, INSERT ... VALUES (...), (...), ..., and LOAD DATA INFILE when adding data to nonempty tables. This variable limits the size of the cache tree in bytes per thread. Setting it to 0 disables this optimization. The default value is 8MB.

  • character_set_client

    System VariableNamecharacter_set_client
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Permitted ValuesTypestring

    The character set for statements that arrive from the client. The session value of this variable is set using the character set requested by the client when the client connects to the server. (Many clients support a --default-character-set option to enable this character set to be specified explicitly. See also Section 10.1.4, “Connection Character Sets and Collations”.) The global value of the variable is used to set the session value in cases when the client-requested value is unknown or not available, or the server is configured to ignore client requests:

    • The client is from a version of MySQL older than MySQL 4.1, and thus does not request a character set.

    • The client requests a character set not known to the server. For example, a Japanese-enabled client requests sjis when connecting to a server not configured with sjis support.

    • mysqld was started with the --skip-character-set-client-handshake option, which causes it to ignore client character set configuration. This reproduces MySQL 4.0 behavior and is useful should you wish to upgrade the server without upgrading all the clients.

    ucs2, utf16, utf16le, and utf32 cannot be used as a client character set, which means that they also do not work for SET NAMES or SET CHARACTER SET.

  • character_set_connection

    System VariableNamecharacter_set_connection
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Permitted ValuesTypestring

    The character set used for literals that do not have a character set introducer and for number-to-string conversion.

  • character_set_database

    System VariableNamecharacter_set_database
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    FootnoteThis option is dynamic, but only the server should set this information. You should not set the value of this variable manually.
    Permitted ValuesTypestring

    The character set used by the default database. The server sets this variable whenever the default database changes. If there is no default database, the variable has the same value as character_set_server.

  • character_set_filesystem

    Command-Line Format--character-set-filesystem=name
    System VariableNamecharacter_set_filesystem
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Permitted ValuesTypestring
    Defaultbinary

    The file system character set. This variable is used to interpret string literals that refer to file names, such as in the LOAD DATA INFILE and SELECT ... INTO OUTFILE statements and the LOAD_FILE() function. Such file names are converted from character_set_client to character_set_filesystem before the file opening attempt occurs. The default value is binary, which means that no conversion occurs. For systems on which multibyte file names are permitted, a different value may be more appropriate. For example, if the system represents file names using UTF-8, set character_set_filesystem to 'utf8'.

  • character_set_results

    System VariableNamecharacter_set_results
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Permitted ValuesTypestring

    The character set used for returning query results such as result sets or error messages to the client.

  • character_set_server

    Command-Line Format--character-set-server
    System VariableNamecharacter_set_server
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Permitted ValuesTypestring
    Defaultlatin1

    The server's default character set.

  • character_set_system

    System VariableNamecharacter_set_system
    Variable ScopeGlobal
    Dynamic VariableNo
    Permitted ValuesTypestring
    Defaultutf8

    The character set used by the server for storing identifiers. The value is always utf8.

  • character_sets_dir

    Command-Line Format--character-sets-dir=path
    System VariableNamecharacter_sets_dir
    Variable ScopeGlobal
    Dynamic VariableNo
    Permitted ValuesTypedirectory name

    The directory where character sets are installed.

  • collation_connection

    System VariableNamecollation_connection
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Permitted ValuesTypestring

    The collation of the connection character set.

  • collation_database

    System VariableNamecollation_database
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    FootnoteThis option is dynamic, but only the server should set this information. You should not set the value of this variable manually.
    Permitted ValuesTypestring

    The collation used by the default database. The server sets this variable whenever the default database changes. If there is no default database, the variable has the same value as collation_server.

  • collation_server

    Command-Line Format--collation-server
    System VariableNamecollation_server
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Permitted ValuesTypestring
    Defaultlatin1_swedish_ci

    The server's default collation.

  • completion_type

    Command-Line Format--completion_type=#
    System VariableNamecompletion_type
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Permitted ValuesTypeenumeration
    DefaultNO_CHAIN
    Valid ValuesNO_CHAIN
    CHAIN
    RELEASE
    0
    1
    2

    The transaction completion type. This variable can take the values shown in the following table. The variable can be assigned using either the name values or corresponding integer values.

    ValueDescription
    NO_CHAIN (or 0)COMMIT and ROLLBACK are unaffected. This is the default value.
    CHAIN (or 1)COMMIT and ROLLBACK are equivalent to COMMIT AND CHAIN and ROLLBACK AND CHAIN, respectively. (A new transaction starts immediately with the same isolation level as the just-terminated transaction.)
    RELEASE (or 2)COMMIT and ROLLBACK are equivalent to COMMIT RELEASE and ROLLBACK RELEASE, respectively. (The server disconnects after terminating the transaction.)

    completion_type affects transactions that begin with START TRANSACTION or BEGIN and end with COMMIT or ROLLBACK. It does not apply to implicit commits resulting from execution of the statements listed in Section 13.3.3, “Statements That Cause an Implicit Commit”. It also does not apply for XA COMMIT, XA ROLLBACK, or when autocommit=1.

  • concurrent_insert

    Command-Line Format--concurrent_insert[=#]
    System VariableNameconcurrent_insert
    Variable ScopeGlobal
    Dynamic VariableYes
    Permitted ValuesTypeenumeration
    DefaultAUTO
    Valid ValuesNEVER
    AUTO
    ALWAYS
    0
    1
    2

    If AUTO (the default), MySQL permits INSERT and SELECT statements to run concurrently for MyISAM tables that have no free blocks in the middle of the data file. If you start mysqld with --skip-new, this variable is set to NEVER.

    This variable can take the values shown in the following table. The variable can be assigned using either the name values or corresponding integer values.

    ValueDescription
    NEVER (or 0)Disables concurrent inserts
    AUTO (or 1)(Default) Enables concurrent insert for MyISAM tables that do not have holes
    ALWAYS (or 2)Enables concurrent inserts for all MyISAM tables, even those that have holes. For a table with a hole, new rows are inserted at the end of the table if it is in use by another thread. Otherwise, MySQL acquires a normal write lock and inserts the row into the hole.

    See also Section 8.10.3, “Concurrent Inserts”.

  • connect_timeout

    Command-Line Format--connect_timeout=#
    System VariableNameconnect_timeout
    Variable ScopeGlobal
    Dynamic VariableYes
    Permitted ValuesTypenumeric
    Default10
    Min Value2
    Max Value31536000

    The number of seconds that the mysqld server waits for a connect packet before responding with Bad handshake. The default value is 10 seconds.

    Increasing the connect_timeout value might help if clients frequently encounter errors of the form Lost connection to MySQL server at 'XXX', system error: errno.

  • core_file

    Introduced5.6.2
    System VariableNamecore_file
    Variable ScopeGlobal
    Dynamic VariableNo
    Permitted ValuesTypeboolean
    DefaultOFF

    Whether to write a core file if the server crashes. This variable is set by the --core-file option. It was added in MySQL 5.6.2.

  • datadir

    Command-Line Format--datadir=path
    System VariableNamedatadir
    Variable ScopeGlobal
    Dynamic VariableNo
    Permitted ValuesTypedirectory name

    The MySQL data directory. This variable can be set with the --datadir option.

  • date_format

    This variable is unused. It is deprecated as of MySQL 5.6.7 and will be removed in a future MySQL release.

  • datetime_format

    This variable is unused. It is deprecated as of MySQL 5.6.7 and will be removed in a future MySQL release.

  • debug

    Command-Line Format--debug[=debug_options]
    System VariableNamedebug
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Permitted Values (Unix)Typestring
    Defaultd:t:i:o,/tmp/mysqld.trace
    Permitted Values (Windows)Typestring
    Defaultd:t:i:O,\mysqld.trace

    This variable indicates the current debugging settings. It is available only for servers built with debugging support. The initial value comes from the value of instances of the --debug option given at server startup. The global and session values may be set at runtime; the SUPER privilege is required, even for the session value.

    Assigning a value that begins with + or - cause the value to added to or subtracted from the current value:

    mysql> SET debug = 'T';
    mysql> SELECT @@debug;
    +---------+
    | @@debug |
    +---------+
    | T       |
    +---------+
    
    mysql> SET debug = '+P';
    mysql> SELECT @@debug;
    +---------+
    | @@debug |
    +---------+
    | P:T     |
    +---------+
    
    mysql> SET debug = '-P';
    mysql> SELECT @@debug;
    +---------+
    | @@debug |
    +---------+
    | T       |
    +---------+
    

    For more information, see Section 24.4.3, “The DBUG Package”.

  • debug_sync

    System VariableNamedebug_sync
    Variable ScopeSession
    Dynamic VariableYes
    Permitted ValuesTypestring

    This variable is the user interface to the Debug Sync facility. Use of Debug Sync requires that MySQL be configured with the -DENABLE_DEBUG_SYNC=1 option (see Section 2.9.4, “MySQL Source-Configuration Options”). If Debug Sync is not compiled in, this system variable is not available.

    The global variable value is read only and indicates whether the facility is enabled. By default, Debug Sync is disabled and the value of debug_sync is OFF. If the server is started with --debug-sync-timeout=N, where N is a timeout value greater than 0, Debug Sync is enabled and the value of debug_sync is ON - current signal followed by the signal name. Also, N becomes the default timeout for individual synchronization points.

    The session value can be read by any user and will have the same value as the global variable. The session value can be set by users that have the SUPER privilege to control synchronization points.

    For a description of the Debug Sync facility and how to use synchronization points, see MySQL Internals: Test Synchronization.

  • default_storage_engine

    Command-Line Format--default-storage-engine=name
    System VariableNamedefault_storage_engine
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Permitted ValuesTypeenumeration
    DefaultInnoDB

    The default storage engine. As of MySQL 5.6.3, this variable sets the storage engine for permanent tables only. To set the storage engine for TEMPORARY tables, set the default_tmp_storage_engine system variable.

    To see which storage engines are available and enabled, use the SHOW ENGINES statement or query the INFORMATION_SCHEMA ENGINES table.

    default_storage_engine should be used in preference to storage_engine, which is deprecated.

    If you disable the default storage engine at server startup, you must set the default engine for both permanent and TEMPORARY tables to a different engine or the server will not start.

  • default_tmp_storage_engine

    Introduced5.6.3
    Command-Line Format--default_tmp_storage_engine=name
    System VariableNamedefault_tmp_storage_engine
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Permitted ValuesTypeenumeration
    DefaultInnoDB

    The default storage engine for TEMPORARY tables (created with CREATE TEMPORARY TABLE). To set the storage engine for permanent tables, set the default_storage_engine system variable.

    If you disable the default storage engine at server startup, you must set the default engine for both permanent and TEMPORARY tables to a different engine or the server will not start.

    default_tmp_storage_engine was added in MySQL 5.6.3.

  • default_week_format

    Command-Line Format--default_week_format=#
    System VariableNamedefault_week_format
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Permitted ValuesTypenumeric
    Default0
    Min Value0
    Max Value7

    The default mode value to use for the WEEK() function. See Section 12.7, “Date and Time Functions”.

  • delay_key_write

    Command-Line Format--delay-key-write[=name]
    System VariableNamedelay_key_write
    Variable ScopeGlobal
    Dynamic VariableYes
    Permitted ValuesTypeenumeration
    DefaultON
    Valid ValuesON
    OFF
    ALL

    This option applies only to MyISAM tables. It can have one of the following values to affect handling of the DELAY_KEY_WRITE table option that can be used in CREATE TABLE statements.

    OptionDescription
    OFFDELAY_KEY_WRITE is ignored.
    ONMySQL honors any DELAY_KEY_WRITE option specified in CREATE TABLE statements. This is the default value.
    ALLAll new opened tables are treated as if they were created with the DELAY_KEY_WRITE option enabled.

    If DELAY_KEY_WRITE is enabled for a table, the key buffer is not flushed for the table on every index update, but only when the table is closed. This speeds up writes on keys a lot, but if you use this feature, you should add automatic checking of all MyISAM tables by starting the server with the --myisam-recover-options option (for example, --myisam-recover-options=BACKUP,FORCE). See Section 5.1.3, “Server Command Options”, and Section 15.2.1, “MyISAM Startup Options”.

    Warning

    If you enable external locking with --external-locking, there is no protection against index corruption for tables that use delayed key writes.

  • delayed_insert_limit

    Deprecated5.6.7
    Command-Line Format--delayed_insert_limit=#
    System VariableNamedelayed_insert_limit
    Variable ScopeGlobal
    Dynamic VariableYes
    Permitted Values (32-bit platforms)Typenumeric
    Default100
    Min Value1
    Max Value4294967295
    Permitted Values (64-bit platforms)Typenumeric
    Default100
    Min Value1
    Max Value18446744073709551615

    After inserting delayed_insert_limit delayed rows into a nontransactional table, the INSERT DELAYED handler thread checks whether there are any SELECT statements pending. If so, it permits them to execute before continuing to insert delayed rows.

    As of MySQL 5.6.7, this system variable is deprecated (because DELAYED inserts are deprecated), and will be removed in a future release.

  • delayed_insert_timeout

    Deprecated5.6.7
    Command-Line Format--delayed_insert_timeout=#
    System VariableNamedelayed_insert_timeout
    Variable ScopeGlobal
    Dynamic VariableYes
    Permitted ValuesTypenumeric
    Default300

    How many seconds an INSERT DELAYED handler thread should wait for INSERT statements before terminating.

    As of MySQL 5.6.7, this system variable is deprecated (because DELAYED inserts are deprecated), and will be removed in a future release.

  • delayed_queue_size

    Deprecated5.6.7
    Command-Line Format--delayed_queue_size=#
    System VariableNamedelayed_queue_size
    Variable ScopeGlobal
    Dynamic VariableYes
    Permitted Values (32-bit platforms)Typenumeric
    Default1000
    Min Value1
    Max Value4294967295
    Permitted Values (64-bit platforms)Typenumeric
    Default1000
    Min Value1
    Max Value18446744073709551615

    This is a per-table limit on the number of rows to queue when handling INSERT DELAYED statements for nontransactional tables. If the queue becomes full, any client that issues an INSERT DELAYED statement waits until there is room in the queue again.

    As of MySQL 5.6.7, this system variable is deprecated (because DELAYED inserts are deprecated), and will be removed in a future release.

  • disconnect_on_expired_password

    Introduced5.6.10
    Command-Line Format--disconnect_on_expired_password=#
    System VariableNamedisconnect_on_expired_password
    Variable ScopeSession
    Dynamic VariableNo
    Permitted ValuesTypeboolean
    DefaultON

    This variable controls how the server handles clients with expired passwords:

    For more information about the interaction of client and server settings relating to expired-password handling, see Section 6.3.6, “Password Expiration and Sandbox Mode”.

    This variable was added in MySQL 5.6.10.

  • div_precision_increment

    Command-Line Format--div_precision_increment=#
    System VariableNamediv_precision_increment
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Permitted ValuesTypenumeric
    Default4
    Min Value0
    Max Value30

    This variable indicates the number of digits by which to increase the scale of the result of division operations performed with the / operator. The default value is 4. The minimum and maximum values are 0 and 30, respectively. The following example illustrates the effect of increasing the default value.

    mysql> SELECT 1/7;
    +--------+
    | 1/7    |
    +--------+
    | 0.1429 |
    +--------+
    mysql> SET div_precision_increment = 12;
    mysql> SELECT 1/7;
    +----------------+
    | 1/7            |
    +----------------+
    | 0.142857142857 |
    +----------------+
    
  • engine_condition_pushdown

    Deprecated5.5.3, by optimizer_switch
    Removed5.6.1
    Command-Line Format--engine-condition-pushdown
    System VariableNameengine_condition_pushdown
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Permitted ValuesTypeboolean
    DefaultON

    This variable was removed in MySQL 5.6.1. Use the engine_condition_pushdown flag of the optimizer_switch variable instead. See Section 8.8.5.2, “Controlling Switchable Optimizations”.

  • end_markers_in_json

    Introduced5.6.5
    System VariableNameend_markers_in_json
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Permitted ValuesTypeboolean
    DefaultOFF

    Whether optimizer JSON output should add end markers.

  • eq_range_index_dive_limit

    Introduced5.6.5
    System VariableNameeq_range_index_dive_limit
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Permitted ValuesTypenumeric
    Default10
    Min Value0
    Max Value4294967295

    This variable indicates the number of equality ranges in an equality comparison condition when the optimizer should switch from using index dives to index statistics in estimating the number of qualifying rows. It applies to evaluation of expressions that have either of these equivalent forms, where the optimizer uses a nonunique index to look up col_name values:

    col_name IN(val1, ..., valN)
    col_name = val1 OR ... OR col_name = valN
    

    In both cases, the expression contains N equality ranges. The optimizer can make row estimates using index dives or index statistics. If eq_range_index_dive_limit is greater than 0, the optimizer uses existing index statistics instead of index dives if there are eq_range_index_dive_limit or more equality ranges. Thus, to permit use of index dives for up to N equality ranges, set eq_range_index_dive_limit to N + 1. Set eq_range_index_dive_limit to 0 to disable use of index statistics and always use index dives regardless of N.

    For more information, see Section 8.2.1.3.3, “Equality Range Optimization of Many-Valued Comparisons”.

    This variable was added in MySQL 5.6.5. Before 5.6.5, the optimizer makes row estimates using index dives in all cases.

    To update table index statistics for best estimates, use ANALYZE TABLE.

  • error_count

    The number of errors that resulted from the last statement that generated messages. This variable is read only. See Section 13.7.5.18, “SHOW ERRORS Syntax”.

  • event_scheduler

    Command-Line Format--event-scheduler[=value]
    System VariableNameevent_scheduler
    Variable ScopeGlobal
    Dynamic VariableYes
    Permitted ValuesTypeenumeration
    DefaultOFF
    Valid ValuesON
    OFF
    DISABLED

    This variable indicates the status of the Event Scheduler; possible values are ON, OFF, and DISABLED, with the default being OFF. This variable and its effects on the Event Scheduler's operation are discussed in greater detail in the Overview section of the Events chapter.

  • expire_logs_days

    Command-Line Format--expire_logs_days=#
    System VariableNameexpire_logs_days
    Variable ScopeGlobal
    Dynamic VariableYes
    Permitted ValuesTypenumeric
    Default0
    Min Value0
    Max Value99

    The number of days for automatic binary log file removal. The default is 0, which means no automatic removal. Possible removals happen at startup and when the binary log is flushed. Log flushing occurs as indicated in Section 5.2, “MySQL Server Logs”.

    To remove binary log files manually, use the PURGE BINARY LOGS statement. See Section 13.4.1.1, “PURGE BINARY LOGS Syntax”.

  • explicit_defaults_for_timestamp

    Introduced5.6.6
    Command-Line Format--explicit_defaults_for_timestamp=#
    System VariableNameexplicit_defaults_for_timestamp
    Variable ScopeSession
    Dynamic VariableNo
    Permitted ValuesTypeboolean
    DefaultFALSE

    In MySQL, the TIMESTAMP data type differs in nonstandard ways from other data types:

    • TIMESTAMP columns not explicitly declared with the NULL attribute are assigned the NOT NULL attribute. (Columns of other data types, if not explicitly declared as NOT NULL, permit NULL values.) Setting such a column to NULL sets it to the current timestamp.

    • The first TIMESTAMP column in a table, if not declared with the NULL attribute or an explicit DEFAULT or ON UPDATE clause, is automatically assigned the DEFAULT CURRENT_TIMESTAMP and ON UPDATE CURRENT_TIMESTAMP attributes.

    • TIMESTAMP columns following the first one, if not declared with the NULL attribute or an explicit DEFAULT clause, are automatically assigned DEFAULT '0000-00-00 00:00:00' (the zero timestamp). For inserted rows that specify no explicit value for such a column, the column is assigned '0000-00-00 00:00:00' and no warning occurs.

    Those nonstandard behaviors remain the default for TIMESTAMP but as of MySQL 5.6.6 are deprecated and this warning appears at startup:

    [Warning] TIMESTAMP with implicit DEFAULT value is deprecated.
    Please use --explicit_defaults_for_timestamp server option (see
    documentation for more details).
    

    As indicated by the warning, to turn off the nonstandard behaviors, enable the new explicit_defaults_for_timestamp system variable at server startup. With this variable enabled, the server handles TIMESTAMP as follows instead:

    • TIMESTAMP columns not explicitly declared as NOT NULL permit NULL values. Setting such a column to NULL sets it to NULL, not the current timestamp.

    • No TIMESTAMP column is assigned the DEFAULT CURRENT_TIMESTAMP or ON UPDATE CURRENT_TIMESTAMP attributes automatically. Those attributes must be explicitly specified.

    • TIMESTAMP columns declared as NOT NULL and without an explicit DEFAULT clause are treated as having no default value. For inserted rows that specify no explicit value for such a column, the result depends on the SQL mode. If strict SQL mode is enabled, an error occurs. If strict SQL mode is not enabled, the column is assigned the implicit default of '0000-00-00 00:00:00' and a warning occurs. This is similar to how MySQL treats other temporal types such as DATETIME.

    Note

    explicit_defaults_for_timestamp is itself deprecated because its only purpose is to permit control over now-deprecated TIMESTAMP behaviors that will be removed in a future MySQL release. When that removal occurs, explicit_defaults_for_timestamp will have no purpose and will be removed as well.

    This variable was added in MySQL 5.6.6.

  • external_user

    System VariableNameexternal_user
    Variable ScopeSession
    Dynamic VariableNo
    Permitted ValuesTypestring

    The external user name used during the authentication process, as set by the plugin used to authenticate the client. With native (built-in) MySQL authentication, or if the plugin does not set the value, this variable is NULL. See Section 6.3.9, “Proxy Users”.

  • flush

    Command-Line Format--flush
    System VariableNameflush
    Variable ScopeGlobal
    Dynamic VariableYes
    Permitted ValuesTypeboolean
    DefaultOFF

    If ON, the server flushes (synchronizes) all changes to disk after each SQL statement. Normally, MySQL does a write of all changes to disk only after each SQL statement and lets the operating system handle the synchronizing to disk. See Section B.5.4.2, “What to Do If MySQL Keeps Crashing”. This variable is set to ON if you start mysqld with the --flush option.

  • flush_time

    Command-Line Format--flush_time=#
    System VariableNameflush_time
    Variable ScopeGlobal
    Dynamic VariableYes
    Permitted ValuesTypenumeric
    Default0
    Min Value0
    Permitted Values (Windows, <= 5.6.5)Typenumeric
    Default1800
    Min Value0
    Permitted Values (Windows, >= 5.6.6)Typenumeric
    Default0
    Min Value0

    If this is set to a nonzero value, all tables are closed every flush_time seconds to free up resources and synchronize unflushed data to disk. This option is best used only on systems with minimal resources. The default is 0 except that before MySQL 5.6.6, the default is 1800 on Windows.

  • foreign_key_checks

    If set to 1 (the default), foreign key constraints for InnoDB tables are checked. If set to 0, such constraints are ignored. Beginning with MySQL Cluster NDB 7.3.2, setting this variable has the same effect on NDB tables as it does for InnoDB tables—previously, the setting was ignored and all such checks were enforced (Bug #14095855). Typically you leave this setting enabled during normal operation, to enforce referential integrity. Disabling foreign key checking can be useful for reloading such tables in an order different from that required by their parent/child relationships. See Section 14.6.6, “InnoDB and FOREIGN KEY Constraints”.

    Setting foreign_key_checks to 0 also affects data definition statements: DROP SCHEMA drops a schema even if it contains tables that have foreign keys that are referred to by tables outside the schema, and DROP TABLE drops tables that have foreign keys that are referred to by other tables.

    Note

    Setting foreign_key_checks to 1 does not trigger a scan of the existing table data. Therefore, rows added to the table while foreign_key_checks = 0 will not be verified for consistency.

  • ft_boolean_syntax

    Command-Line Format--ft_boolean_syntax=name
    System VariableNameft_boolean_syntax
    Variable ScopeGlobal
    Dynamic VariableYes
    Permitted ValuesTypestring
    Default+ -><()~*:""&|

    The list of operators supported by boolean full-text searches performed using IN BOOLEAN MODE. See Section 12.9.2, “Boolean Full-Text Searches”.

    The default variable value is '+ -><()~*:""&|'. The rules for changing the value are as follows:

    • Operator function is determined by position within the string.

    • The replacement value must be 14 characters.

    • Each character must be an ASCII nonalphanumeric character.

    • Either the first or second character must be a space.

    • No duplicates are permitted except the phrase quoting operators in positions 11 and 12. These two characters are not required to be the same, but they are the only two that may be.

    • Positions 10, 13, and 14 (which by default are set to :, &, and |) are reserved for future extensions.

  • ft_max_word_len

    Command-Line Format--ft_max_word_len=#
    System VariableNameft_max_word_len
    Variable ScopeGlobal
    Dynamic VariableNo
    Permitted ValuesTypenumeric
    Min Value10

    The maximum length of the word to be included in a MyISAM FULLTEXT index.

    Note

    FULLTEXT indexes on MyISAM tables must be rebuilt after changing this variable. Use REPAIR TABLE tbl_name QUICK.

  • ft_min_word_len

    Command-Line Format--ft_min_word_len=#
    System VariableNameft_min_word_len
    Variable ScopeGlobal
    Dynamic VariableNo
    Permitted ValuesTypenumeric
    Default4
    Min Value1

    The minimum length of the word to be included in a MyISAM FULLTEXT index.

    Note

    FULLTEXT indexes on MyISAM tables must be rebuilt after changing this variable. Use REPAIR TABLE tbl_name QUICK.

  • ft_query_expansion_limit

    Command-Line Format--ft_query_expansion_limit=#
    System VariableNameft_query_expansion_limit
    Variable ScopeGlobal
    Dynamic VariableNo
    Permitted ValuesTypenumeric
    Default20
    Min Value0
    Max Value1000

    The number of top matches to use for full-text searches performed using WITH QUERY EXPANSION.

  • ft_stopword_file

    Command-Line Format--ft_stopword_file=file_name
    System VariableNameft_stopword_file
    Variable ScopeGlobal
    Dynamic VariableNo
    Permitted ValuesTypefile name

    The file from which to read the list of stopwords for full-text searches on MyISAM tables. The server looks for the file in the data directory unless an absolute path name is given to specify a different directory. All the words from the file are used; comments are not honored. By default, a built-in list of stopwords is used (as defined in the storage/myisam/ft_static.c file). Setting this variable to the empty string ('') disables stopword filtering. See also Section 12.9.4, “Full-Text Stopwords”.

    Note

    FULLTEXT indexes on MyISAM tables must be rebuilt after changing this variable or the contents of the stopword file. Use REPAIR TABLE tbl_name QUICK.

  • general_log

    Command-Line Format--general-log
    System VariableNamegeneral_log
    Variable ScopeGlobal
    Dynamic VariableYes
    Permitted ValuesTypeboolean
    DefaultOFF

    Whether the general query log is enabled. The value can be 0 (or OFF) to disable the log or 1 (or ON) to enable the log. The default value depends on whether the --general_log option is given. The destination for log output is controlled by the log_output system variable; if that value is NONE, no log entries are written even if the log is enabled.

  • general_log_file

    Command-Line Format--general-log-file=file_name
    System VariableNamegeneral_log_file
    Variable ScopeGlobal
    Dynamic VariableYes
    Permitted ValuesTypefile name
    Defaulthost_name.log

    The name of the general query log file. The default value is host_name.log, but the initial value can be changed with the --general_log_file option.

  • group_concat_max_len

    Command-Line Format--group_concat_max_len=#
    System VariableNamegroup_concat_max_len
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Permitted Values (32-bit platforms)Typenumeric
    Default1024
    Min Value4
    Max Value4294967295
    Permitted Values (64-bit platforms)Typenumeric
    Default1024
    Min Value4
    Max Value18446744073709551615

    The maximum permitted result length in bytes for the GROUP_CONCAT() function. The default is 1024.

  • have_compress

    YES if the zlib compression library is available to the server, NO if not. If not, the COMPRESS() and UNCOMPRESS() functions cannot be used.

  • have_crypt

    YES if the crypt() system call is available to the server, NO if not. If not, the ENCRYPT() function cannot be used.

  • have_csv

    YES if mysqld supports CSV tables, NO if not.

    This variable was removed in MySQL 5.6.1. Use SHOW ENGINES instead.

  • have_dynamic_loading

    YES if mysqld supports dynamic loading of plugins, NO if not.

  • have_geometry

    YES if the server supports spatial data types, NO if not.

  • have_innodb

    YES if mysqld supports InnoDB tables. DISABLED if --skip-innodb is used.

    This variable was removed in MySQL 5.6.1. Use SHOW ENGINES instead.

  • have_openssl

    This variable is an alias for have_ssl.

  • have_partitioning

    YES if mysqld supports partitioning.

    This variable was removed in MySQL 5.6.1. Use SHOW PLUGINS instead. For more information, see Chapter 19, Partitioning.

  • have_profiling

    YES if statement profiling capability is present, NO if not. If present, the profiling system variable controls whether this capability is enabled or disabled. See Section 13.7.5.32, “SHOW PROFILES Syntax”.

    This variable is deprecated in MySQL 5.6.8 and will be removed in a future MySQL release.

  • have_query_cache

    YES if mysqld supports the query cache, NO if not.

  • have_rtree_keys

    YES if RTREE indexes are available, NO if not. (These are used for spatial indexes in MyISAM tables.)

  • have_ssl

    YES if mysqld supports SSL connections, NO if not. DISABLED indicates that the server was compiled with SSL support, but was not started with the appropriate --ssl-xxx options. For more information, see Section 6.3.10.2, “Configuring MySQL for SSL”.

  • have_symlink

    YES if symbolic link support is enabled, NO if not. This is required on Unix for support of the DATA DIRECTORY and INDEX DIRECTORY table options, and on Windows for support of data directory symlinks. If the server is started with the --skip-symbolic-links option, the value is DISABLED.

  • host_cache_size

    Introduced5.6.5
    System VariableNamehost_cache_size
    Variable ScopeGlobal
    Dynamic VariableYes
    Permitted Values (<= 5.6.7)Typenumeric
    Default128
    Min Value0
    Max Value65536
    Permitted Values (>= 5.6.8)Typenumeric
    Default-1 (autosized)
    Min Value0
    Max Value65536

    The size of the internal host cache (see Section 8.11.5.2, “DNS Lookup Optimization and the Host Cache”). Setting the size to 0 disables the host cache. Changing the cache size at runtime implicitly causes a FLUSH HOSTS operation to clear the host cache and truncate the host_cache table.

    The default value is 128, plus 1 for a value of max_connections up to 500, plus 1 for every increment of 20 over 500 in the max_connections value, capped to a limit of 2000. Before MySQL 5.6.8, the default is 128.

    Use of --skip-host-cache is similar to setting the host_cache_size system variable to 0, but host_cache_size is more flexible because it can also be used to resize, enable, or disable the host cache at runtime, not just at server startup.

    If you start the server with --skip-host-cache, that does not prevent changes to the value of host_cache_size, but such changes have no effect and the cache is not re-enabled even if host_cache_size is set larger than 0.

    This variable was added in MySQL 5.6.5.

  • hostname

    System VariableNamehostname
    Variable ScopeGlobal
    Dynamic VariableNo
    Permitted ValuesTypestring

    The server sets this variable to the server host name at startup.

  • identity

    This variable is a synonym for the last_insert_id variable. It exists for compatibility with other database systems. You can read its value with SELECT @@identity, and set it using SET identity.

  • ignore_db_dirs

    Introduced5.6.3
    System VariableNameignore_db_dirs
    Variable ScopeGlobal
    Dynamic VariableNo
    Permitted ValuesTypestring

    A comma-separated list of names that are not considered as database directories in the data directory. The value is set from any instances of --ignore-db-dir given at server startup.

    This variable was added in MySQL 5.6.3.

  • init_connect

    Command-Line Format--init-connect=name
    System VariableNameinit_connect
    Variable ScopeGlobal
    Dynamic VariableYes
    Permitted ValuesTypestring

    A string to be executed by the server for each client that connects. The string consists of one or more SQL statements, separated by semicolon characters. For example, each client session begins by default with autocommit mode enabled. For older servers (before MySQL 5.5.8), there is no global autocommit system variable to specify that autocommit should be disabled by default, but as a workaround init_connect can be used to achieve the same effect:

    SET GLOBAL init_connect='SET autocommit=0';
    

    The init_connect variable can also be set on the command line or in an option file. To set the variable as just shown using an option file, include these lines:

    [mysqld]
    init_connect='SET autocommit=0'
    

    The content of init_connect is not executed for users that have the SUPER privilege. This is done so that an erroneous value for init_connect does not prevent all clients from connecting. For example, the value might contain a statement that has a syntax error, thus causing client connections to fail. Not executing init_connect for users that have the SUPER privilege enables them to open a connection and fix the init_connect value.

  • init_file

    Command-Line Format--init-file=file_name
    System VariableNameinit_file
    Variable ScopeGlobal
    Dynamic VariableNo
    Permitted ValuesTypefile name

    The name of the file specified with the --init-file option when you start the server. This should be a file containing SQL statements that you want the server to execute when it starts. Each statement must be on a single line and should not include comments. No statement terminator such as ;, \g, or \G should be given at the end of each statement.

  • innodb_xxx

    InnoDB system variables are listed in Section 14.12, “InnoDB Startup Options and System Variables”. These variables control many aspects of storage, memory use, and I/O patterns for InnoDB tables, and are especially important now that InnoDB is the default storage engine.

  • insert_id

    The value to be used by the following INSERT or ALTER TABLE statement when inserting an AUTO_INCREMENT value. This is mainly used with the binary log.

  • interactive_timeout

    Command-Line Format--interactive_timeout=#
    System VariableNameinteractive_timeout
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Permitted ValuesTypenumeric
    Default28800
    Min Value1

    The number of seconds the server waits for activity on an interactive connection before closing it. An interactive client is defined as a client that uses the CLIENT_INTERACTIVE option to mysql_real_connect(). See also wait_timeout.

  • join_buffer_size

    Command-Line Format--join_buffer_size=#
    System VariableNamejoin_buffer_size
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Permitted Values (Windows, <= 5.6.5)Typenumeric
    Default131072
    Min Value128
    Max Value4294967295
    Permitted Values (Other, 32-bit platforms, <= 5.6.5)Typenumeric
    Default131072
    Min Value128
    Max Value4294967295
    Permitted Values (Other, 64-bit platforms, <= 5.6.5)Typenumeric
    Default131072
    Min Value128
    Max Value18446744073709547520
    Permitted Values (Windows, >= 5.6.6)Typenumeric
    Default262144
    Min Value128
    Max Value4294967295
    Permitted Values (Other, 32-bit platforms, >= 5.6.6)Typenumeric
    Default262144
    Min Value128
    Max Value4294967295
    Permitted Values (Other, 64-bit platforms, >= 5.6.6)Typenumeric
    Default262144
    Min Value128
    Max Value18446744073709547520

    The minimum size of the buffer that is used for plain index scans, range index scans, and joins that do not use indexes and thus perform full table scans. Normally, the best way to get fast joins is to add indexes. Increase the value of join_buffer_size to get a faster full join when adding indexes is not possible. One join buffer is allocated for each full join between two tables. For a complex join between several tables for which indexes are not used, multiple join buffers might be necessary.

    Unless Batched Key Access (BKA) is used, there is no gain from setting the buffer larger than required to hold each matching row, and all joins allocate at least the minimum size, so use caution in setting this variable to a large value globally. It is better to keep the global setting small and change to a larger setting only in sessions that are doing large joins. Memory allocation time can cause substantial performance drops if the global size is larger than needed by most queries that use it.

    When BKA is used, the value of join_buffer_size defines how large the batch of keys is in each request to the storage engine. The larger the buffer, the more sequential access will be to the right hand table of a join operation, which can significantly improve performance.

    The default is 256KB as of MySQL 5.6.6, 128KB before that. The maximum permissible setting for join_buffer_size is 4GB–1. Larger values are permitted for 64-bit platforms (except 64-bit Windows, for which large values are truncated to 4GB–1 with a warning).

    For additional information about join buffering, see Section 8.2.1.10, “Nested-Loop Join Algorithms”. For information about Batched Key Access, see Section 8.2.1.14, “Block Nested-Loop and Batched Key Access Joins”.

  • keep_files_on_create

    Command-Line Format--keep_files_on_create=#
    System VariableNamekeep_files_on_create
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Permitted ValuesTypeboolean
    DefaultOFF

    If a MyISAM table is created with no DATA DIRECTORY option, the .MYD file is created in the database directory. By default, if MyISAM finds an existing .MYD file in this case, it overwrites it. The same applies to .MYI files for tables created with no INDEX DIRECTORY option. To suppress this behavior, set the keep_files_on_create variable to ON (1), in which case MyISAM will not overwrite existing files and returns an error instead. The default value is OFF (0).

    If a MyISAM table is created with a DATA DIRECTORY or INDEX DIRECTORY option and an existing .MYD or .MYI file is found, MyISAM always returns an error. It will not overwrite a file in the specified directory.

  • key_buffer_size

    Command-Line Format--key_buffer_size=#
    System VariableNamekey_buffer_size
    Variable ScopeGlobal
    Dynamic VariableYes
    Permitted Values (32-bit platforms)Typenumeric
    Default8388608
    Min Value8
    Max Value4294967295
    Permitted Values (64-bit platforms)Typenumeric
    Default8388608
    Min Value8
    Max ValueOS_PER_PROCESS_LIMIT

    Index blocks for MyISAM tables are buffered and are shared by all threads. key_buffer_size is the size of the buffer used for index blocks. The key buffer is also known as the key cache.

    The maximum permissible setting for key_buffer_size is 4GB–1 on 32-bit platforms. Larger values are permitted for 64-bit platforms. The effective maximum size might be less, depending on your available physical RAM and per-process RAM limits imposed by your operating system or hardware platform. The value of this variable indicates the amount of memory requested. Internally, the server allocates as much memory as possible up to this amount, but the actual allocation might be less.

    You can increase the value to get better index handling for all reads and multiple writes; on a system whose primary function is to run MySQL using the MyISAM storage engine, 25% of the machine's total memory is an acceptable value for this variable. However, you should be aware that, if you make the value too large (for example, more than 50% of the machine's total memory), your system might start to page and become extremely slow. This is because MySQL relies on the operating system to perform file system caching for data reads, so you must leave some room for the file system cache. You should also consider the memory requirements of any other storage engines that you may be using in addition to MyISAM.

    For even more speed when writing many rows at the same time, use LOCK TABLES. See Section 8.2.2.1, “Speed of INSERT Statements”.

    You can check the performance of the key buffer by issuing a SHOW STATUS statement and examining the Key_read_requests, Key_reads, Key_write_requests, and Key_writes status variables. (See Section 13.7.5, “SHOW Syntax”.) The Key_reads/Key_read_requests ratio should normally be less than 0.01. The Key_writes/Key_write_requests ratio is usually near 1 if you are using mostly updates and deletes, but might be much smaller if you tend to do updates that affect many rows at the same time or if you are using the DELAY_KEY_WRITE table option.

    The fraction of the key buffer in use can be determined using key_buffer_size in conjunction with the Key_blocks_unused status variable and the buffer block size, which is available from the key_cache_block_size system variable:

    1 - ((Key_blocks_unused * key_cache_block_size) / key_buffer_size)
    

    This value is an approximation because some space in the key buffer is allocated internally for administrative structures. Factors that influence the amount of overhead for these structures include block size and pointer size. As block size increases, the percentage of the key buffer lost to overhead tends to decrease. Larger blocks results in a smaller number of read operations (because more keys are obtained per read), but conversely an increase in reads of keys that are not examined (if not all keys in a block are relevant to a query).

    It is possible to create multiple MyISAM key caches. The size limit of 4GB applies to each cache individually, not as a group. See Section 8.9.2, “The MyISAM Key Cache”.

  • key_cache_age_threshold

    Command-Line Format--key_cache_age_threshold=#
    System VariableNamekey_cache_age_threshold
    Variable ScopeGlobal
    Dynamic VariableYes
    Permitted Values (32-bit platforms)Typenumeric
    Default300
    Min Value100
    Max Value4294967295
    Permitted Values (64-bit platforms)Typenumeric
    Default300
    Min Value100
    Max Value18446744073709551615

    This value controls the demotion of buffers from the hot sublist of a key cache to the warm sublist. Lower values cause demotion to happen more quickly. The minimum value is 100. The default value is 300. See Section 8.9.2, “The MyISAM Key Cache”.

  • key_cache_block_size

    Command-Line Format--key_cache_block_size=#
    System VariableNamekey_cache_block_size
    Variable ScopeGlobal
    Dynamic VariableYes
    Permitted ValuesTypenumeric
    Default1024
    Min Value512
    Max Value16384

    The size in bytes of blocks in the key cache. The default value is 1024. See Section 8.9.2, “The MyISAM Key Cache”.

  • key_cache_division_limit

    Command-Line Format--key_cache_division_limit=#
    System VariableNamekey_cache_division_limit
    Variable ScopeGlobal
    Dynamic VariableYes
    Permitted ValuesTypenumeric
    Default100
    Min Value1
    Max Value100

    The division point between the hot and warm sublists of the key cache buffer list. The value is the percentage of the buffer list to use for the warm sublist. Permissible values range from 1 to 100. The default value is 100. See Section 8.9.2, “The MyISAM Key Cache”.

  • large_files_support

    System VariableNamelarge_files_support
    Variable ScopeGlobal
    Dynamic VariableNo

    Whether mysqld was compiled with options for large file support.

  • large_pages

    Command-Line Format--large-pages
    System VariableNamelarge_pages
    Variable ScopeGlobal
    Dynamic VariableNo
    Platform SpecificLinux
    Permitted Values (Linux)Typeboolean
    DefaultFALSE

    Whether large page support is enabled (via the --large-pages option). See Section 8.11.4.2, “Enabling Large Page Support”.

  • large_page_size

    System VariableNamelarge_page_size
    Variable ScopeGlobal
    Dynamic VariableNo
    Permitted Values (Linux)Typenumeric
    Default0

    If large page support is enabled, this shows the size of memory pages. Currently, large memory pages are supported only on Linux; on other platforms, the value of this variable is always 0. See Section 8.11.4.2, “Enabling Large Page Support”.

  • last_insert_id

    The value to be returned from LAST_INSERT_ID(). This is stored in the binary log when you use LAST_INSERT_ID() in a statement that updates a table. Setting this variable does not update the value returned by the mysql_insert_id() C API function.

  • lc_messages

    Command-Line Format--lc-messages=name
    System VariableNamelc_messages
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Permitted ValuesTypestring
    Defaulten_US

    The locale to use for error messages. The default is en_US. The server converts the argument to a language name and combines it with the value of lc_messages_dir to produce the location for the error message file. See Section 10.2, “Setting the Error Message Language”.

  • lc_messages_dir

    Command-Line Format--lc-messages-dir=dir_name
    System VariableNamelc_messages_dir
    Variable ScopeGlobal
    Dynamic VariableNo
    Permitted ValuesTypedirectory name

    The directory where error messages are located. The server uses the value together with the value of lc_messages to produce the location for the error message file. See Section 10.2, “Setting the Error Message Language”.

  • lc_time_names

    System VariableNamelc_time_names
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Permitted ValuesTypestring

    This variable specifies the locale that controls the language used to display day and month names and abbreviations. This variable affects the output from the DATE_FORMAT(), DAYNAME() and MONTHNAME() functions. Locale names are POSIX-style values such as 'ja_JP' or 'pt_BR'. The default value is 'en_US' regardless of your system's locale setting. For further information, see Section 10.7, “MySQL Server Locale Support”.

  • license

    System VariableNamelicense
    Variable ScopeGlobal
    Dynamic VariableNo
    Permitted ValuesTypestring
    DefaultGPL

    The type of license the server has.

  • local_infile

    System VariableNamelocal_infile
    Variable ScopeGlobal
    Dynamic VariableYes
    Permitted ValuesTypeboolean

    Whether LOCAL is supported for LOAD DATA INFILE statements. If this variable is disabled, clients cannot use LOCAL in LOAD DATA statements. See Section 6.1.6, “Security Issues with LOAD DATA LOCAL”.

  • lock_wait_timeout

    Command-Line Format--lock_wait_timeout=#
    System VariableNamelock_wait_timeout
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Permitted ValuesTypenumeric
    Default31536000
    Min Value1
    Max Value31536000

    This variable specifies the timeout in seconds for attempts to acquire metadata locks. The permissible values range from 1 to 31536000 (1 year). The default is 31536000.

    This timeout applies to all statements that use metadata locks. These include DML and DDL operations on tables, views, stored procedures, and stored functions, as well as LOCK TABLES, FLUSH TABLES WITH READ LOCK, and HANDLER statements.

    This timeout does not apply to implicit accesses to system tables in the mysql database, such as grant tables modified by GRANT or REVOKE statements or table logging statements. The timeout does apply to system tables accessed directly, such as with SELECT or UPDATE.

    The timeout value applies separately for each metadata lock attempt. A given statement can require more than one lock, so it is possible for the statement to block for longer than the lock_wait_timeout value before reporting a timeout error. When lock timeout occurs, ER_LOCK_WAIT_TIMEOUT is reported.

    lock_wait_timeout does not apply to delayed inserts, which always execute with a timeout of 1 year. This is done to avoid unnecessary timeouts because a session that issues a delayed insert receives no notification of delayed insert timeouts.

  • locked_in_memory

    System VariableNamelocked_in_memory
    Variable ScopeGlobal
    Dynamic VariableNo

    Whether mysqld was locked in memory with --memlock.

  • log

    Deprecated5.1.29, by general-log
    Removed5.6.1
    Command-Line Format--log[=file_name]
    System VariableNamelog
    Variable ScopeGlobal
    Dynamic VariableYes
    Permitted ValuesTypefile name

    This variable removed in MySQL 5.6.1. Use general_log instead.

  • log_bin_trust_function_creators

    Command-Line Format--log-bin-trust-function-creators
    System VariableNamelog_bin_trust_function_creators
    Variable ScopeGlobal
    Dynamic VariableYes
    Permitted ValuesTypeboolean
    DefaultFALSE

    This variable applies when binary logging is enabled. It controls whether stored function creators can be trusted not to create stored functions that will cause unsafe events to be written to the binary log. If set to 0 (the default), users are not permitted to create or alter stored functions unless they have the SUPER privilege in addition to the CREATE ROUTINE or ALTER ROUTINE privilege. A setting of 0 also enforces the restriction that a function must be declared with the DETERMINISTIC characteristic, or with the READS SQL DATA or NO SQL characteristic. If the variable is set to 1, MySQL does not enforce these restrictions on stored function creation. This variable also applies to trigger creation. See Section 20.7, “Binary Logging of Stored Programs”.

  • log_error

    Command-Line Format--log-error[=file_name]
    System VariableNamelog_error
    Variable ScopeGlobal
    Dynamic VariableNo
    Permitted ValuesTypefile name

    The location of the error log, or empty if the server is writing error message to the standard error output. See Section 5.2.2, “The Error Log”.

  • log_output

    Command-Line Format--log-output=name
    System VariableNamelog_output
    Variable ScopeGlobal
    Dynamic VariableYes
    Permitted ValuesTypeset
    DefaultFILE
    Valid ValuesTABLE
    FILE
    NONE

    The destination for general query log and slow query log output. The value can be a comma-separated list of one or more of the words TABLE (log to tables), FILE (log to files), or NONE (do not log to tables or files). The default value is FILE. NONE, if present, takes precedence over any other specifiers. If the value is NONE log entries are not written even if the logs are enabled. If the logs are not enabled, no logging occurs even if the value of log_output is not NONE. For more information, see Section 5.2.1, “Selecting General Query and Slow Query Log Output Destinations”.

  • log_queries_not_using_indexes

    Command-Line Format--log-queries-not-using-indexes
    System VariableNamelog_queries_not_using_indexes
    Variable ScopeGlobal
    Dynamic VariableYes
    Permitted ValuesTypeboolean
    DefaultOFF

    Whether queries that do not use indexes are logged to the slow query log. See Section 5.2.5, “The Slow Query Log”.

  • log_slow_admin_statements

    Introduced5.6.11
    System VariableNamelog_slow_admin_statements
    Variable ScopeGlobal
    Dynamic VariableYes
    Permitted ValuesTypeboolean
    DefaultOFF

    Include slow administrative statements in the statements written to the slow query log. Administrative statements include ALTER TABLE, ANALYZE TABLE, CHECK TABLE, CREATE INDEX, DROP INDEX, OPTIMIZE TABLE, and REPAIR TABLE.

    This variable was added in MySQL 5.6.11 as a replacement for the --log-slow-admin-statements option. The system variable can be set on the command line or in option files the same way as the option, so there is no need for any changes at server startup, but the system variable also makes it possible to examine or set the value at runtime.

  • log_slow_queries

    Deprecated5.1.29, by slow-query-log
    Removed5.6.1
    Command-Line Format--log-slow-queries[=name]
    System VariableNamelog_slow_queries
    Variable ScopeGlobal
    Dynamic VariableYes
    Permitted ValuesTypeboolean

    This variable was removed in MySQL 5.6.1. Use slow_query_log instead.

  • log_throttle_queries_not_using_indexes

    Introduced5.6.5
    System VariableNamelog_throttle_queries_not_using_indexes
    Variable ScopeGlobal
    Dynamic VariableYes
    Permitted ValuesTypenumeric
    Default0

    If log_queries_not_using_indexes is enabled, the log_throttle_queries_not_using_indexes variable limits the number of such queries per minute that can be written to the slow query log. A value of 0 (the default) means no limit. For more information, see Section 5.2.5, “The Slow Query Log”.

    This variable was added in MySQL 5.6.5.

  • log_warnings

    Command-Line Format--log-warnings[=#]
    System Variable (<= 5.6.3)Namelog_warnings
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    System Variable (>= 5.6.4)Namelog_warnings
    Variable ScopeGlobal
    Dynamic VariableYes
    Permitted Values (32-bit platforms)Typenumeric
    Default1
    Min Value0
    Max Value4294967295
    Permitted Values (64-bit platforms)Typenumeric
    Default1
    Min Value0
    Max Value18446744073709551615

    Whether to produce additional warning messages to the error log. This variable is enabled (1) by default and can be disabled by setting it to 0. The server logs messages about statements that are unsafe for statement-based logging if the value is greater than 0. Aborted connections and access-denied errors for new connection attempts are logged if the value is greater than 1.

  • long_query_time

    Command-Line Format--long_query_time=#
    System VariableNamelong_query_time
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Permitted ValuesTypenumeric
    Default10
    Min Value0

    If a query takes longer than this many seconds, the server increments the Slow_queries status variable. If the slow query log is enabled, the query is logged to the slow query log file. This value is measured in real time, not CPU time, so a query that is under the threshold on a lightly loaded system might be above the threshold on a heavily loaded one. The minimum and default values of long_query_time are 0 and 10, respectively. The value can be specified to a resolution of microseconds. For logging to a file, times are written including the microseconds part. For logging to tables, only integer times are written; the microseconds part is ignored. See Section 5.2.5, “The Slow Query Log”.

  • low_priority_updates

    Command-Line Format--low-priority-updates
    System VariableNamelow_priority_updates
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Permitted ValuesTypeboolean
    DefaultFALSE

    If set to 1, all INSERT, UPDATE, DELETE, and LOCK TABLE WRITE statements wait until there is no pending SELECT or LOCK TABLE READ on the affected table. This affects only storage engines that use only table-level locking (such as MyISAM, MEMORY, and MERGE).

  • lower_case_file_system

    System VariableNamelower_case_file_system
    Variable ScopeGlobal
    Dynamic VariableNo
    Permitted ValuesTypeboolean

    This variable describes the case sensitivity of file names on the file system where the data directory is located. OFF means file names are case sensitive, ON means they are not case sensitive. This variable is read only because it reflects a file system attribute and setting it would have no effect on the file system.

  • lower_case_table_names

    Command-Line Format--lower_case_table_names[=#]
    System VariableNamelower_case_table_names
    Variable ScopeGlobal
    Dynamic VariableNo
    Permitted ValuesTypenumeric
    Default0
    Min Value0
    Max Value2

    If set to 0, table names are stored as specified and comparisons are case sensitive. If set to 1, table names are stored in lowercase on disk and comparisons are not case sensitive. If set to 2, table names are stored as given but compared in lowercase. This option also applies to database names and table aliases. For additional information, see Section 9.2.2, “Identifier Case Sensitivity”.

    You should not set this variable to 0 if you are running MySQL on a system that has case-insensitive file names (such as Windows or OS X). If you set this variable to 0 on such a system and access MyISAM tablenames using different lettercases, index corruption may result. On Windows the default value is 1. On OS X, the default value is 2.

    If you are using InnoDB tables, you should set this variable to 1 on all platforms to force names to be converted to lowercase.

    The setting of this variable in MySQL 5.6 affects the behavior of replication filtering options with regard to case sensitivity. This is a change from previous versions of MySQL. (Bug #51639) See Section 17.2.3, “How Servers Evaluate Replication Filtering Rules”, for more information.

    In previous versions of MySQL, using different settings for lower_case_table_names on replication masters and slaves could cause replication to fail when the slave used a case-sensitive file system. This issue is resolved in MySQL 5.6.1. For more information, see Section 17.4.1.34, “Replication and Variables”.

  • max_allowed_packet

    Command-Line Format--max_allowed_packet=#
    System VariableNamemax_allowed_packet
    Variable ScopeGlobal
    Dynamic VariableYes
    Permitted Values (<= 5.6.5)Typenumeric
    Default1048576
    Min Value1024
    Max Value1073741824
    Permitted Values (>= 5.6.6)Typenumeric
    Default4194304
    Min Value1024
    Max Value1073741824

    The maximum size of one packet or any generated/intermediate string, or any parameter sent by the mysql_stmt_send_long_data() C API function. The default is 4MB as of MySQL 5.6.6, 1MB before that.

    The packet message buffer is initialized to net_buffer_length bytes, but can grow up to max_allowed_packet bytes when needed. This value by default is small, to catch large (possibly incorrect) packets.

    You must increase this value if you are using large BLOB columns or long strings. It should be as big as the largest BLOB you want to use. The protocol limit for max_allowed_packet is 1GB. The value should be a multiple of 1024; nonmultiples are rounded down to the nearest multiple.

    When you change the message buffer size by changing the value of the max_allowed_packet variable, you should also change the buffer size on the client side if your client program permits it. The default max_allowed_packet value built in to the client library is 1GB, but individual client programs might override this. For example, mysql and mysqldump have defaults of 16MB and 24MB, respectively. They also enable you to change the client-side value by setting max_allowed_packet on the command line or in an option file.

    The session value of this variable is read only.

  • max_connect_errors

    Command-Line Format--max_connect_errors=#
    System VariableNamemax_connect_errors
    Variable ScopeGlobal
    Dynamic VariableYes
    Permitted Values (32-bit platforms, <= 5.6.5)Typenumeric
    Default10
    Min Value1
    Max Value4294967295
    Permitted Values (64-bit platforms, <= 5.6.5)Typenumeric
    Default10
    Min Value1
    Max Value18446744073709551615
    Permitted Values (32-bit platforms, >= 5.6.6)Typenumeric
    Default100
    Min Value1
    Max Value4294967295
    Permitted Values (64-bit platforms, >= 5.6.6)Typenumeric
    Default100
    Min Value1
    Max Value18446744073709551615

    If more than this many successive connection requests from a host are interrupted without a successful connection, the server blocks that host from further connections. You can unblock blocked hosts by flushing the host cache. To do so, issue a FLUSH HOSTS statement or execute a mysqladmin flush-hosts command. If a connection is established successfully within fewer than max_connect_errors attempts after a previous connection was interrupted, the error count for the host is cleared to zero. However, once a host is blocked, flushing the host cache is the only way to unblock it. The default is 100 as of MySQL 5.6.6, 10 before that.

  • max_connections

    Command-Line Format--max_connections=#
    System VariableNamemax_connections
    Variable ScopeGlobal
    Dynamic VariableYes
    Permitted ValuesTypenumeric
    Default151
    Min Value1
    Max Value16384
    Permitted ValuesTypenumeric
    Default151
    Min Value1
    Max Value100000

    The maximum permitted number of simultaneous client connections. By default, this is 151. See Section B.5.2.7, “Too many connections”, for more information.

    Increasing this value increases the number of file descriptors that mysqld requires. If the required number of descriptors are not available, the server reduces the value of max_connections. See Section 8.4.3.1, “How MySQL Opens and Closes Tables”, for comments on file descriptor limits.

    Connections refused because the max_connections limit is reached increment the Connection_errors_max_connections status variable.

  • max_delayed_threads

    Deprecated5.6.7
    Command-Line Format--max_delayed_threads=#
    System VariableNamemax_delayed_threads
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Permitted ValuesTypenumeric
    Default20
    Min Value0
    Max Value16384

    Do not start more than this number of threads to handle INSERT DELAYED statements for nontransactional tables. If you try to insert data into a new table after all INSERT DELAYED threads are in use, the row is inserted as if the DELAYED attribute was not specified. If you set this to 0, MySQL never creates a thread to handle DELAYED rows; in effect, this disables DELAYED entirely.

    For the SESSION value of this variable, the only valid values are 0 or the GLOBAL value.

    As of MySQL 5.6.7, this system variable is deprecated (because DELAYED inserts are deprecated), and will be removed in a future release.

  • max_error_count

    Command-Line Format--max_error_count=#
    System VariableNamemax_error_count
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Permitted ValuesTypenumeric
    Default64
    Min Value0
    Max Value65535

    The maximum number of error, warning, and note messages to be stored for display by the SHOW ERRORS and SHOW WARNINGS statements. This is the same as the number of condition areas in the diagnostics area, and thus the number of conditions that can be inspected by GET DIAGNOSTICS.

  • max_heap_table_size

    Command-Line Format--max_heap_table_size=#
    System VariableNamemax_heap_table_size
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Permitted Values (32-bit platforms)Typenumeric
    Default16777216
    Min Value16384
    Max Value4294967295
    Permitted Values (64-bit platforms)Typenumeric
    Default16777216
    Min Value16384
    Max Value1844674407370954752

    This variable sets the maximum size to which user-created MEMORY tables are permitted to grow. The value of the variable is used to calculate MEMORY table MAX_ROWS values. Setting this variable has no effect on any existing MEMORY table, unless the table is re-created with a statement such as CREATE TABLE or altered with ALTER TABLE or TRUNCATE TABLE. A server restart also sets the maximum size of existing MEMORY tables to the global max_heap_table_size value.

    This variable is also used in conjunction with tmp_table_size to limit the size of internal in-memory tables. See Section 8.4.4, “How MySQL Uses Internal Temporary Tables”.

    max_heap_table_size is not replicated. See Section 17.4.1.21, “Replication and MEMORY Tables”, and Section 17.4.1.34, “Replication and Variables”, for more information.

  • max_insert_delayed_threads

    Deprecated5.6.7
    System VariableNamemax_insert_delayed_threads
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Permitted ValuesTypenumeric

    This variable is a synonym for max_delayed_threads.

    As of MySQL 5.6.7, this system variable is deprecated (because DELAYED inserts are deprecated), and will be removed in a future release.

  • max_join_size

    Command-Line Format--max_join_size=#
    System VariableNamemax_join_size
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Permitted ValuesTypenumeric
    Default18446744073709551615
    Min Value1
    Max Value18446744073709551615

    Do not permit statements that probably need to examine more than max_join_size rows (for single-table statements) or row combinations (for multiple-table statements) or that are likely to do more than max_join_size disk seeks. By setting this value, you can catch statements where keys are not used properly and that would probably take a long time. Set it if your users tend to perform joins that lack a WHERE clause, that take a long time, or that return millions of rows.

    Setting this variable to a value other than DEFAULT resets the value of sql_big_selects to 0. If you set the sql_big_selects value again, the max_join_size variable is ignored.

    If a query result is in the query cache, no result size check is performed, because the result has previously been computed and it does not burden the server to send it to the client.

  • max_length_for_sort_data

    Command-Line Format--max_length_for_sort_data=#
    System VariableNamemax_length_for_sort_data
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Permitted ValuesTypenumeric
    Default1024
    Min Value4
    Max Value8388608

    The cutoff on the size of index values that determines which filesort algorithm to use. See Section 8.2.1.15, “ORDER BY Optimization”.

  • max_prepared_stmt_count

    Command-Line Format--max_prepared_stmt_count=#
    System VariableNamemax_prepared_stmt_count
    Variable ScopeGlobal
    Dynamic VariableYes
    Permitted ValuesTypenumeric
    Default16382
    Min Value0
    Max Value1048576

    This variable limits the total number of prepared statements in the server. (The sum of the number of prepared statements across all sessions.) It can be used in environments where there is the potential for denial-of-service attacks based on running the server out of memory by preparing huge numbers of statements. If the value is set lower than the current number of prepared statements, existing statements are not affected and can be used, but no new statements can be prepared until the current number drops below the limit. The default value is 16,382. The permissible range of values is from 0 to 1 million. Setting the value to 0 disables prepared statements.

  • max_relay_log_size

    Command-Line Format--max_relay_log_size=#
    System VariableNamemax_relay_log_size
    Variable ScopeGlobal
    Dynamic VariableYes
    Permitted ValuesTypenumeric
    Default0
    Min Value0
    Max Value1073741824

    If a write by a replication slave to its relay log causes the current log file size to exceed the value of this variable, the slave rotates the relay logs (closes the current file and opens the next one). If max_relay_log_size is 0, the server uses max_binlog_size for both the binary log and the relay log. If max_relay_log_size is greater than 0, it constrains the size of the relay log, which enables you to have different sizes for the two logs. You must set max_relay_log_size to between 4096 bytes and 1GB (inclusive), or to 0. The default value is 0. See Section 17.2.1, “Replication Implementation Details”.

  • max_seeks_for_key

    Command-Line Format--max_seeks_for_key=#
    System VariableNamemax_seeks_for_key
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Permitted Values (32-bit platforms)Typenumeric
    Default4294967295
    Min Value1
    Max Value4294967295
    Permitted Values (64-bit platforms)Typenumeric
    Default18446744073709551615
    Min Value1
    Max Value18446744073709551615

    Limit the assumed maximum number of seeks when looking up rows based on a key. The MySQL optimizer assumes that no more than this number of key seeks are required when searching for matching rows in a table by scanning an index, regardless of the actual cardinality of the index (see Section 13.7.5.23, “SHOW INDEX Syntax”). By setting this to a low value (say, 100), you can force MySQL to prefer indexes instead of table scans.

  • max_sort_length

    Command-Line Format--max_sort_length=#
    System VariableNamemax_sort_length
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Permitted ValuesTypenumeric
    Default1024
    Min Value4
    Max Value8388608

    The number of bytes to use when sorting data values. Only the first max_sort_length bytes of each value are used; the rest are ignored.

    As of MySQL 5.6.9, max_sort_length is ignored for integer, decimal, floating-point, and temporal data types.

  • max_sp_recursion_depth

    Command-Line Format--max_sp_recursion_depth[=#]
    System VariableNamemax_sp_recursion_depth
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Permitted ValuesTypenumeric
    Default0
    Max Value255

    The number of times that any given stored procedure may be called recursively. The default value for this option is 0, which completely disables recursion in stored procedures. The maximum value is 255.

    Stored procedure recursion increases the demand on thread stack space. If you increase the value of max_sp_recursion_depth, it may be necessary to increase thread stack size by increasing the value of thread_stack at server startup.

  • max_tmp_tables

    This variable is unused. It is deprecated as of MySQL 5.6.7 and will be removed in a future MySQL release.

  • max_user_connections

    Command-Line Format--max_user_connections=#
    System VariableNamemax_user_connections
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Permitted ValuesTypenumeric
    Default0
    Min Value0
    Max Value4294967295

    The maximum number of simultaneous connections permitted to any given MySQL user account. A value of 0 (the default) means no limit.

    This variable has a global value that can be set at server startup or runtime. It also has a read-only session value that indicates the effective simultaneous-connection limit that applies to the account associated with the current session. The session value is initialized as follows:

    • If the user account has a nonzero MAX_USER_CONNECTIONS resource limit, the session max_user_connections value is set to that limit.

    • Otherwise, the session max_user_connections value is set to the global value.

    Account resource limits are specified using the GRANT statement. See Section 6.3.4, “Setting Account Resource Limits”, and Section 13.7.1.4, “GRANT Syntax”.

  • max_write_lock_count

    Command-Line Format--max_write_lock_count=#
    System VariableNamemax_write_lock_count
    Variable ScopeGlobal
    Dynamic VariableYes
    Permitted Values (32-bit platforms)Typenumeric
    Default4294967295
    Min Value1
    Max Value4294967295
    Permitted Values (64-bit platforms)Typenumeric
    Default18446744073709551615
    Min Value1
    Max Value18446744073709551615

    After this many write locks, permit some pending read lock requests to be processed in between.

  • metadata_locks_cache_size

    Introduced5.6.4
    System VariableNamemetadata_locks_cache_size
    Variable ScopeGlobal
    Dynamic VariableNo
    Permitted ValuesTypenumeric
    Default1024
    Min Value1
    Max Value1048576

    The size of the metadata locks cache. The server uses this cache to avoid creation and destruction of synchronization objects. This is particularly helpful on systems where such operations are expensive, such as Windows XP. This variable was added in MySQL 5.6.4.

  • metadata_locks_hash_instances

    Introduced5.6.8
    System VariableNamemetadata_locks_hash_instances
    Variable ScopeGlobal
    Dynamic VariableNo
    Permitted ValuesTypenumeric
    Default8
    Min Value1
    Max Value1024

    The set of metadata locks can be partitioned into separate hashes to permit connections accessing different objects to use different locking hashes and reduce contention. The metadata_locks_hash_instances system variable specifies the number of hashes (default 8). This variable was added in MySQL 5.6.8.

  • min_examined_row_limit

    Command-Line Format--min-examined-row-limit=#
    System VariableNamemin_examined_row_limit
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Permitted Values (32-bit platforms)Typenumeric
    Default0
    Min Value0
    Max Value4294967295
    Permitted Values (64-bit platforms)Typenumeric
    Default0
    Min Value0
    Max Value18446744073709551615

    Queries that examine fewer than this number of rows are not logged to the slow query log.

  • multi_range_count

    Command-Line Format--multi_range_count=#
    System VariableNamemulti_range_count
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Permitted ValuesTypenumeric
    Default256
    Min Value1
    Max Value4294967295

    The maximum number of ranges to send to a table handler at once during range selects. The default value is 256. Sending multiple ranges to a handler at once can improve the performance of certain selects dramatically. This is especially true for the NDBCLUSTER table handler, which needs to send the range requests to all nodes. Sending a batch of those requests at once reduces communication costs significantly.

    This variable was removed in MySQL 5.6.7.

  • myisam_data_pointer_size

    Command-Line Format--myisam_data_pointer_size=#
    System VariableNamemyisam_data_pointer_size
    Variable ScopeGlobal
    Dynamic VariableYes
    Permitted ValuesTypenumeric
    Default6
    Min Value2
    Max Value7

    The default pointer size in bytes, to be used by CREATE TABLE for MyISAM tables when no MAX_ROWS option is specified. This variable cannot be less than 2 or larger than 7. The default value is 6. See Section B.5.2.12, “The table is full”.

  • myisam_max_sort_file_size

    Command-Line Format--myisam_max_sort_file_size=#
    System VariableNamemyisam_max_sort_file_size
    Variable ScopeGlobal
    Dynamic VariableYes
    Permitted Values (32-bit platforms)Typenumeric
    Default2147483648
    Permitted Values (64-bit platforms)Typenumeric
    Default9223372036854775807

    The maximum size of the temporary file that MySQL is permitted to use while re-creating a MyISAM index (during REPAIR TABLE, ALTER TABLE, or LOAD DATA INFILE). If the file size would be larger than this value, the index is created using the key cache instead, which is slower. The value is given in bytes.

    If MyISAM index files exceed this size and disk space is available, increasing the value may help performance. The space must be available in the file system containing the directory where the original index file is located.

  • myisam_mmap_size

    Command-Line Format--myisam_mmap_size=#
    System VariableNamemyisam_mmap_size
    Variable ScopeGlobal
    Dynamic VariableNo
    Permitted Values (32-bit platforms)Typenumeric
    Default4294967295
    Min Value7
    Max Value4294967295
    Permitted Values (64-bit platforms)Typenumeric
    Default18446744073709551615
    Min Value7
    Max Value18446744073709551615

    The maximum amount of memory to use for memory mapping compressed MyISAM files. If many compressed MyISAM tables are used, the value can be decreased to reduce the likelihood of memory-swapping problems.

  • myisam_recover_options

    System VariableNamemyisam_recover_options
    Variable ScopeGlobal
    Dynamic VariableNo

    The value of the --myisam-recover-options option. See Section 5.1.3, “Server Command Options”.

  • myisam_repair_threads

    Command-Line Format--myisam_repair_threads=#
    System VariableNamemyisam_repair_threads
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Permitted Values (32-bit platforms)Typenumeric
    Default1
    Min Value1
    Max Value4294967295
    Permitted Values (64-bit platforms)Typenumeric
    Default1
    Min Value1
    Max Value18446744073709551615

    If this value is greater than 1, MyISAM table indexes are created in parallel (each index in its own thread) during the Repair by sorting process. The default value is 1.

    Note

    Multi-threaded repair is still beta-quality code.

  • myisam_sort_buffer_size

    Command-Line Format--myisam_sort_buffer_size=#
    System VariableNamemyisam_sort_buffer_size
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Permitted Values (Windows)Typenumeric
    Default8388608
    Min Value4096
    Max Value4294967295
    Permitted Values (Other, 32-bit platforms)Typenumeric
    Default8388608
    Min Value4096
    Max Value4294967295
    Permitted Values (Other, 64-bit platforms)Typenumeric
    Default8388608
    Min Value4096
    Max Value18446744073709551615

    The size of the buffer that is allocated when sorting MyISAM indexes during a REPAIR TABLE or when creating indexes with CREATE INDEX or ALTER TABLE.

    The maximum permissible setting for myisam_sort_buffer_size is 4GB–1. Larger values are permitted for 64-bit platforms (except 64-bit Windows, for which large values are truncated to 4GB–1 with a warning).

  • myisam_stats_method

    Command-Line Format--myisam_stats_method=name
    System VariableNamemyisam_stats_method
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Permitted ValuesTypeenumeration
    Defaultnulls_unequal
    Valid Valuesnulls_equal
    nulls_unequal
    nulls_ignored

    How the server treats NULL values when collecting statistics about the distribution of index values for MyISAM tables. This variable has three possible values, nulls_equal, nulls_unequal, and nulls_ignored. For nulls_equal, all NULL index values are considered equal and form a single value group that has a size equal to the number of NULL values. For nulls_unequal, NULL values are considered unequal, and each NULL forms a distinct value group of size 1. For nulls_ignored, NULL values are ignored.

    The method that is used for generating table statistics influences how the optimizer chooses indexes for query execution, as described in Section 8.3.7, “InnoDB and MyISAM Index Statistics Collection”.

  • myisam_use_mmap

    Command-Line Format--myisam_use_mmap
    System VariableNamemyisam_use_mmap
    Variable ScopeGlobal
    Dynamic VariableYes
    Permitted ValuesTypeboolean
    DefaultOFF

    Use memory mapping for reading and writing MyISAM tables.

  • named_pipe

    System VariableNamenamed_pipe
    Variable ScopeGlobal
    Dynamic VariableNo
    Platform SpecificWindows
    Permitted Values (Windows)Typeboolean
    DefaultOFF

    (Windows only.) Indicates whether the server supports connections over named pipes.

  • net_buffer_length

    Command-Line Format--net_buffer_length=#
    System VariableNamenet_buffer_length
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Permitted ValuesTypenumeric
    Default16384
    Min Value1024
    Max Value1048576

    Each client thread is associated with a connection buffer and result buffer. Both begin with a size given by net_buffer_length but are dynamically enlarged up to max_allowed_packet bytes as needed. The result buffer shrinks to net_buffer_length after each SQL statement.

    This variable should not normally be changed, but if you have very little memory, you can set it to the expected length of statements sent by clients. If statements exceed this length, the connection buffer is automatically enlarged. The maximum value to which net_buffer_length can be set is 1MB.

    The session value of this variable is read only.

  • net_read_timeout

    Command-Line Format--net_read_timeout=#
    System VariableNamenet_read_timeout
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Permitted ValuesTypenumeric
    Default30
    Min Value1

    The number of seconds to wait for more data from a connection before aborting the read. When the server is reading from the client, net_read_timeout is the timeout value controlling when to abort. When the server is writing to the client, net_write_timeout is the timeout value controlling when to abort. See also slave_net_timeout.

  • net_retry_count

    Command-Line Format--net_retry_count=#
    System VariableNamenet_retry_count
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Permitted Values (32-bit platforms)Typenumeric
    Default10
    Min Value1
    Max Value4294967295
    Permitted Values (64-bit platforms)Typenumeric
    Default10
    Min Value1
    Max Value18446744073709551615

    If a read or write on a communication port is interrupted, retry this many times before giving up. This value should be set quite high on FreeBSD because internal interrupts are sent to all threads.

  • net_write_timeout

    Command-Line Format--net_write_timeout=#
    System VariableNamenet_write_timeout
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Permitted ValuesTypenumeric
    Default60
    Min Value1

    The number of seconds to wait for a block to be written to a connection before aborting the write. See also net_read_timeout.

  • new

    Command-Line Format--new
    System VariableNamenew
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Disabled byskip-new
    Permitted ValuesTypeboolean
    DefaultFALSE

    This variable was used in MySQL 4.0 to turn on some 4.1 behaviors, and is retained for backward compatibility. In MySQL 5.6, its value is always OFF.

  • old

    Command-Line Format--old
    System VariableNameold
    Variable ScopeGlobal
    Dynamic VariableNo

    old is a compatibility variable. It is disabled by default, but can be enabled at startup to revert the server to behaviors present in older versions.

    Currently, when old is enabled, it changes the default scope of index hints to that used prior to MySQL 5.1.17. That is, index hints with no FOR clause apply only to how indexes are used for row retrieval and not to resolution of ORDER BY or GROUP BY clauses. (See Section 13.2.9.3, “Index Hint Syntax”.) Take care about enabling this in a replication setup. With statement-based binary logging, having different modes for the master and slaves might lead to replication errors.

  • old_alter_table

    Command-Line Format--old-alter-table
    System VariableNameold_alter_table
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Permitted ValuesTypeboolean
    DefaultOFF

    When this variable is enabled, the server does not use the optimized method of processing an ALTER TABLE operation. It reverts to using a temporary table, copying over the data, and then renaming the temporary table to the original, as used by MySQL 5.0 and earlier. For more information on the operation of ALTER TABLE, see Section 13.1.7, “ALTER TABLE Syntax”.

  • old_passwords