When you are preparing to bring a system back into the participating group after it has left, it is helpful to understand the coordination that occurs among the systems that are already participating in the group. You might see delays in the availability of the entering system because of activity occurring elsewhere in the sysplex. Although it is possible to bring up multiple systems simultaneously, when they reach the point of z/OS UNIX initialization, their processing is serialized so as to allow only one system at a time to initialize z/OS UNIX.

Before it rejoins the participating group, a system processes all the file systems that are listed in the current hierarchy of the participating group. It also attempts to reclaim any unowned file systems that it previously owned when it was part of the participating group. It does not attempt to reclaim those file systems that were successfully moved or recovered to another system in the sysplex.

During initialization, any new MOUNT statements in the BPXPRMxx parmlib member are processed, which makes those file systems available for use within the participating group after they are successfully mounted.

While a system is initializing in a sysplex, critical file systems that are necessary for initialization to complete successfully might become unavailable due to a system outage. When a system is removed from the sysplex, there is a window of time during which any file systems it owned will become inaccessible to other systems. This window of time occurs while other systems are being notified of the system's exit from the sysplex and before they start the cleanup for that system.

Ideally, ownership of critical file systems will have been moved to other systems before the system exits. If that has not happened, there will be a window of time during which these critical file systems are unowned. If the initializing system requires access to these critical file systems during this window, there will likely be mount failures that prevent the initialization from completing successfully. To avoid this situation, you must make sure that any system that is being removed from the sysplex does not own any critical file systems.