Follow these steps to perform a controlled cutover in which the originating instance and a replicating instance switch roles. Such a step is necessary to test cutover or to bring the originating instance down for maintenance. In the following steps, A is the former originating instance and new replicating instance, while B is the former replicating instance and new originating instance.
Choose a time when database update rates are low to minimize the chances clients may time out and retry their messages, and when no batch processes are running.
The external system responsible for originating/replicating status identification should be made aware that Site B should now be the originating instance and Site A should now be the replicating instance. If the messaging layer between clients and servers differs from the external control mechanism, command it to route messages to the replicating instance. There may be a need to hold messages briefly during the cutover.
On A:
Stop the application servers.
Shut down the Source Server with an appropriate timeout. The timeout should be long enough to replicate pending transactions to the replicating instance, but not too long to cause clients to conclude that the application is not available. The GT.M default Source Server wait period is up to 120 seconds.
Wait for B to become functional as the originating instance, and then query B (using -EDITINSTANCE -SHOW) for the journal sequence number when it became the originating instance, and roll back to this number. Transactions that are rolled off the originating instance become "non-replicated transactions" that must subsequently be reconciled on B, either automatically or manually.
Create new journal files.
Start the passive Source Server, and then the Receiver Server.
Start the passive application servers, if appropriate.
On B:
Shut down the Receiver Server with an appropriate timeout.
Create new journal files.
Make the passive Source Server active.
Start the application servers (if they were previously passive, make them active).
If the state of the database indicates that batch operations were in process, restart batch operations.
Begin accepting online transactions.