Ch 03: Monitoring InnoDB Transactions

Information Schema INNODB_TRX

…most dedicated source of information about InnoDB transactions.

Since autocommitting is enabled, there can only be one statement in the transaction (an explicit START TRANSACTION disables autocommitting).

INNODB can skip:

trx_autocommit_non_locking=1

InnoDBMonitor

SHOW ENGINE INNODB STATUS\G

INNODB_METRICS and sys.metrics

information_schema.INNODB_METRICS
   subsystem='transaction'

The most important metric is trx_rseg_history_len because it shows how far behind the purge from the undo logs is.

SELECT variable_value
    FROM sys.metrics
    WHERE
      type='InnoDB Metrics - transaction'
    AND
      variable_name='trx_rseg_history_len';