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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 5.1.7, “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

Parameter Old Default New Default Version
back_log 50 Autosized using max_connections 5.6.6
binlog_checksum NONE CRC32 5.6.6
--binlog-row-event-max-size 1024 8192 5.6.6
flush_time 1800 (on Windows) 0 5.6.6
host_cache_size 128 Autosized using max_connections 5.6.8
innodb_autoextend_increment 8 64 5.6.6
innodb_buffer_pool_instances 1 8 (platform dependent) 5.6.6
innodb_concurrency_tickets 500 5000 5.6.6
innodb_data_file_path ibdata1:10M:autoextend ibdata1:12M:autoextend 5.6.7
innodb_file_per_table 0 1 5.6.6
innodb_log_file_size 5MB 48MB 5.6.8
innodb_old_blocks_time 0 1000 5.6.6
innodb_open_files 300 Autosized using innodb_file_per_table, table_open_cache 5.6.6
innodb_stats_on_metadata ON OFF 5.6.6
join_buffer_size 128KB 256KB 5.6.6
max_allowed_packet 1MB 4MB 5.6.6
max_connect_errors 10 100 5.6.6
open_files_limit 0 Autosized using max_connections 5.6.8
performance_schema OFF ON 5.6.6
performance_schema_events_waits_history_long_size 10000 Autosized 5.6.6
performance_schema_events_waits_history_size 10 Autosized 5.6.6
performance_schema_max_cond_instances 1000 Autosized 5.6.6
performance_schema_max_file_instances 10000 Autosized 5.6.6
performance_schema_max_mutex_instances 1000000 Autosized 5.6.6
performance_schema_max_rwlock_instances 1000000 Autosized 5.6.6
performance_schema_max_table_handles 100000 Autosized 5.6.6
performance_schema_max_table_instances 50000 Autosized 5.6.6
performance_schema_max_thread_instances 1000 Autosized 5.6.6
query_cache_size 0 1M 5.6.8
query_cache_type ON OFF 5.6.8
secure_auth OFF ON 5.6.7
sql_mode '' (empty string) NO_ENGINE_SUBSTITUTION 5.6.6
sync_master_info 0 10000 5.6.6
sync_relay_log 0 10000 5.6.6
sync_relay_log_info 0 10000 5.6.6
table_definition_cache 400 Autosized using table_open_cache 5.6.8
table_open_cache 400 2000 5.6.8
thread_cache_size 0 Autosized using max_connections 5.6.8

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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