The seven 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).

Note that the Information Schema tables are themselves plugins to the MySQL server. As such they need to be INSTALLed as described in Chapter 9, Installing the InnoDB Plugin. If they are installed, but the InnoDB storage engine plugin is not installed, these tables appear to be empty.

Following is a description of the new Information Schema tables introduced in the InnoDB Plugin, and some examples of their use.