What happens when a STOP,IMMED is issued to bring down XCOM
With STOP,IMMED, all shutdown processing (closing the history and RRDS files, etc) is DONE except the following:
Transfers are just stopped - not suspended. No cleanup is done. To the partner it just looks like the other server went down. When it comes back up, processing will restart for type=schedule transfers (given that retries are configured). Partial datasets being written on MVS will not have an EOF on them, but the restart will attempt to reposition into the file with a POINT macro (which does not require the EOF). If it cannot, it will restart from the beginning.
TYPE=EXECUTE transfers will have to be cleaned up manually.
The partner will handle the transfer in the same way it would if the z/OS server went down.
XCOM does not wait on the PSO subtask - XCOM just takes it down.