MySQL 5.7 Reference Manual Including MySQL NDB Cluster 7.5 and NDB Cluster 7.6

16.2.4 Relay Log and Replication Metadata Repositories

A replica server creates several repositories of information to use for the replication process:

The connection metadata repository and applier metadata repository are collectively known as the replication metadata repositories. For information about these, see Section, “Replication Metadata Repositories”.

Making replication resilient to unexpected halts.  The mysql.slave_master_info and mysql.slave_relay_log_info tables are created using the transactional storage engine InnoDB. Updates to the replica's applier metadata repository table are committed together with the transactions, meaning that the replica's progress information recorded in that repository is always consistent with what has been applied to the database, even in the event of an unexpected server halt. For information on the combination of settings on the replica that is most resilient to unexpected halts, see Section 16.3.2, “Handling an Unexpected Halt of a Replica”.