13.7.6. InnoDB INFORMATION_SCHEMA tables

The INFORMATION_SCHEMA is a MySQL feature that helps you monitor server activity to diagnose capacity and performance issues. Several InnoDB-related INFORMATION_SCHEMA tables (INNODB_CMP, INNODB_CMP_RESET, INNODB_CMPMEM, INNODB_CMPMEM_RESET, INNODB_TRX, INNODB_LOCKS and INNODB_LOCK_WAITS) contain live information about compressed InnoDB tables, the compressed InnoDB buffer pool, all transactions currently executing inside InnoDB, the locks that transactions hold and those that are blocking transactions waiting for access to a resource (a table or row).

The Information Schema tables are themselves plugins to the MySQL server, and must be activated by INSTALL statements. If they are installed, but the InnoDB storage engine plugin is not installed, these tables appear to be empty.

This section describes the InnoDB-related Information Schema tables and shows some examples of their use.

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