MySQL Backup cannot lock log tables (4033178)

Attempts to lock a MySQL log table will fail. With default backup options, this will generate warning messages in the logs that will cause the backup to finish in a state "Completed with warnings". The warnings will be similar to:

Warning 2014/03/13 09:22:06 94 Data Plugin mysqlsrv Unable to lock the table [general_log]. This table will be ignored.
Warning 2014/03/13 09:22:06 94 Data Plugin mysqlsrv Unable to lock the table [slow_log]. This table will be ignored.

The general query log is a log of every SQL query received from a client, as well as each client connect and disconnect. It's a record of every query received by the server. The mysql.general_log table stores the contents of the General Query Log.

The slow query log is a record of SQL queries that took a long time to perform. The mysql.slow_log table stores the contents of the Slow Query Log.

MySQL Log tables cannot be locked by MySQL. It is not possible to lock them.

As a solution you can avoid generating this warning message in the Plugin Options set by set the logging action for Locked tables to "Complete without Warnings - Saveset Retained"

Other workarounds are:

Unchecking in the Plugin Options the backup option "Lock All Tables with Read Access During Backup to Prevent Loss of Transactions".  Unchecking this option will allow the log table structure to be backed up, but not the contents. Please be aware that this will have consequences for other tables that are being backed up as they will not be requested to be locked.

Alternatively, It may also be possible to manually unselect the log tables from the backup selection.