The takeover flow

You can determine if you want a takeover to proceed automatically or for it to proceed only with your approval.

If you want a takeover to proceed automatically, specify AUTO=YES in the DFSHSBxx member of IMS.PROCLIB. When IMS detects a takeover condition, it does not give you the option of deciding whether a takeover is needed. You receive message DFS3890I saying that a takeover was requested, and the alternate subsystem takes over the workload from the active subsystem.

If you want a takeover to proceed only with your approval, specify AUTO=NO (the default) in the DFSHSBxx member of IMS.PROCLIB. When IMS detects a takeover condition, you receive message DFS3869 saying that the active subsystem might have failed. You must decide whether to proceed with a takeover. To initiate a takeover, issue the /SWITCH SYSTEM ACTIVE [FORCE] command from the active subsystem if you can. Otherwise, issue the /SWITCH SYSTEM FORCE command from the alternate subsystem.

Good communication between operators for the active and alternate subsystems is essential.