What To Do When DMan Replication Status is Red

The master server writes each incoming command to a binlog file. The slave server processes each line of the file in queue. DMan monitors this process for several factors that would indicate that replication is not working or falling behind.

Slave is behind master N seconds

When the slave server starts to fall behind, the DMan status will report the difference in time. This could be due to network latency or I/O problems on the slave or master. Monitor the delta time between the slave and master and ensure it is getting smaller and not larger. If the time that the slave is behind continues to grow you will need to evaluate the I/O problem.

Error - Unable to process N

Sometimes the slave comes across a command in the master binlog file that it cannot process. When this happens the slave stops processing the queue and if left for a while the slave can get very behind in the queue. Evaluate the line that was unable to process on the slave, take corrective steps, and run the Resynchronize Your Replication Servers procedure below. Before you do the full restore though you can try skipping the next 1 or 2 SQL statements to see if you can resolve the problem that way.

Resynchronize Your Replication Servers

If your replication has been blocked by a command line that cannot process on the slave server, it may have gotten out of synch to an extent that the easiest way is to resynch with a data duplication. To do this simply follow the original instructions to backup the master and restore to the slave found on the Running A Backup Server for Bannister Lake Products with DMan Backup in the section that starts with: Making a Copy of the Primary Database For Import On the Backup Server