When you issue the VARY XCF,system-name,OFFLINE command, MVS™ notifies all groups, through their member group routines, that the system is to be removed from the sysplex. Multisystem applications that are not members of a group can also be notified of a system being removed from the sysplex through ENF event code 35. It is an application program's responsibility to ensure that its remaining members on the other systems in the sysplex can continue processing when a system is removed from the sysplex.

If the system is re-IPLed into the sysplex, MVS notifies all groups, through their member group routines, that the system is added to the sysplex. Multisystem applications that are not members of an XCF group can be notified of a system joining the sysplex through ENF event code 35.