Database replication requires before-image journaling to be enabled and turned ON. If it is OFF, GT.M turns it on when replication is turned on.

A GT.M process writes journal records to a journal buffer and then flushes them to a disk. The process writes the updated journal records to a shared memory segment called the Journal Pool that is shared by all processes using the same Global Directory.

The Source Server process transports each record from the Journal Pool to the secondary system via a TCP/IP connection.