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https://dev.mysql.com/doc/refman/8.0/en/performance-schema-startup-configuration.html
To use the MySQL Performance Schema, it must be enabled at server startup to enable event collection to occur. For example, use these lines in the server my.cnf file: [mysqld] performance_schema=ON If the server is unable to allocate any internal ...To enable or disable it explicitly, start the server with the performance_schema variable set to an appropriate ...
https://dev.mysql.com/doc/refman/8.0/en/checksum-table.html
For example, the storage format for temporal types such as TIME, DATETIME, and TIMESTAMP changed in MySQL 5.6 prior to MySQL 5.6.5, so if a 5.5 table is upgraded to MySQL 5.6, the checksum value may change. For large tables, this could take a long ...[QUICK | EXTENDED] CHECKSUM TABLE reports a checksum for the contents of a ...
https://dev.mysql.com/doc/refman/8.0/en/clone-plugin-concurrent-ddl.html
Prior to MySQL 8.0.27, DDL operations on the donor and recipient MySQL Server instances, including TRUNCATE TABLE, are not permitted during a cloning operation. The clone_ddl_timeout variable defines the time in seconds on the donor and recipient ...A workaround is to use dedicated donor instances, which can accommodate DDL operations being blocked while data is ...
https://dev.mysql.com/doc/refman/8.0/en/host-cache.html
For example, to set the size to 100 at startup, put these lines in the server my.cnf file: [mysqld] host_cache_size=200 To change the size to 300 at runtime, do this: SET GLOBAL host_cache_size=300; Setting host_cache_size to 0, either at server ...
https://dev.mysql.com/doc/refman/8.0/en/innodb-benefits.html
InnoDB tables have the following benefits: If the server unexpectedly exits because of a hardware or software issue, regardless of what was happening in the database at the time, you don't need to do anything special after restarting the database.
https://dev.mysql.com/doc/refman/8.0/en/myisamchk-general-options.html
This option is available only if MySQL was built using WITH_DEBUG. MySQL release binaries provided by Oracle are not built using this option. If you are running mysqld with external locking disabled, the table can be locked only by another myisamchk ... The options described in this section can be used for any type of table maintenance operation performed by ...
https://dev.mysql.com/doc/refman/8.0/en/performance-schema-data-locks-table.html
Example data lock information: mysql> SELECT * FROM performance_schema.data_locks\G *************************** 1. Use the data_locks table to help diagnose performance problems that occur during times of heavy concurrent load. Lock ID formats are ...For information about which lock requests are blocked by which held locks, see Section 29.12.13.2, “The data_lock_waits ...
https://dev.mysql.com/doc/refman/8.0/en/performance-schema-variables-info-table.html
PERSISTED The variable was set from a server-specific mysqld-auto.cnf option file. SERVER The variable was set from a server-specific $MYSQL_HOME/my.cnf option file. For details about how MYSQL_HOME is set, see Section 6.2.2.2, “Using Option ...
https://dev.mysql.com/doc/refman/8.0/en/replication-mode-change-online-enable-gtids.html
Beginning with MySQL 8.0.23, you can set up replication channels to assign GTIDs to replicated transactions that do not already have any. Before you start, ensure that the servers meet the following pre-conditions: All servers in your topology must ... This section describes how to enable GTID transactions, and optionally auto-positioning, on servers that are already online and using anonymous ...
https://dev.mysql.com/doc/refman/8.0/en/replication-semisync-interface.html
To check the current values of the status variables for semisynchronous replication, use SHOW VARIABLES: mysql> SHOW VARIABLES LIKE 'rpl_semi_sync%'; Beginning with MySQL 8.0.26, new versions of the source and replica plugins are supplied, which ...