V11.5 Update Guide

Replication ReSync

A fast fix for occasional situations when a loss of connection causes a target file becomes out-of-sync with the source.

The new Replication ReSync feature allows you to resynchronize a target "replica file" based on the current "source file" with minimum impact in runtime. This feature also allows you to add a new file to a running replication environment.

In This Section Synchronize with repadm resync Add a new file to a running replication environment

Synchronize with repadm resync

Ideally, the target file in a replication environment would never be out-of-sync with the source. In some situations, the target server or the Replication Agent goes down or loses its connection. When all parts of the system are up again and the connections are reestablished, the Replication Agent is able to catch-up with all the updates that must be applied from the moment that it stopped replicating. Although it may take some time to apply the missing updates from the backlog, it should not miss any. Unfortunately, some problems could happen in this process, making it possible that the replica file might get out-of-sync. Some examples:

• A lost transaction log file from the source side that was not applied to the target, making it impossible to bring the target copy back in sync.
• A conflict while applying the modification to the target (perhaps an inadvertent update to the target while replication was inactive).

The Replication ReSync feature provides a way to stop replication on one or more files in a replicated environment and resynchronize them. It copies "current files" from the source server to the target server and then restarts the replication on these files.

The administrator can use repadm -c resync and repadm -c resyncclean to manage the resync operation. The new modes allow the user to indicate the name of the source file to be synchronized. A text file with a list of source file names can be provided in case of multiple files to be synchronized. Based on the source file name, the Replication Agent identifies the target file based on the existing redirect rules.