In the above diagram, some XLogs of SYSTEM A may not be sent to the remote server (SYSTEM B) when the SYSTEM A has a failure. In this case, the system has to fail over to SYSTEM B, but SYSTEM B needs those unsent XLogs to start the service, otherwise, data in between those systems will be inconsistent. This can be achieved if SYSTEM B is able to access the log files of SYSTEM A and apply them locally.
How to use Offline Replicator?
Follow the steps below if you need to use Offline Replicator feature.
Mount a volume with the access enabled for SYSTEM-B
Create Offline Replicator on SYSTEM-B
Execute SQL to start offline replication
Status of Offline Replicator becomes "stop" once it completes its work.
You can start the fail over procedure after checking this status.
To learn more, refer to this manual