Programming Considerations

Consider the following when writing your group user routine:

Because the group user routine runs in SRB mode, it cannot issue any SVCs. You might want to queue work to one or more tasks for processing and post the tasks when needed.
A member might consider having a group user routine, even if the member is the only member of a group that is running on a single-system sysplex. With a group user routine, the member can be notified of system events.
If you plan to have your group user routine maintain a table of systems, groups, and members in the sysplex, you should consider serializing the use of this table with other units of work that require access to it.
XCF schedules the group user routine for only one event at a time. By having other units of work available to process actions that are time consuming, you can avoid missing events.
You should design your group user routine to ignore unknown event codes rather than allowing an unknown event code to abnormally terminate your program. This makes your program independent of future MVS™ releases that might introduce additional event codes.