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MySQL 5.6 Reference Manual
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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 5.1.5, “Server System Variables”, and Section 14.14, “InnoDB Startup Options and System Variables”. Any of these default settings can be overridden by specifying an explicit value at server startup.

Table 5.1 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.


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