The overhead required to operate CMEM is insignificant because
Every WTO message is passed to CMEM by MVS.
CMEM only tracks $HASP001, $HASP100 and $HASP395 messages (under JES2) or IAT6101, IAT6108, IEF403I, IEF404I, IEF450I, and IEF4531 messages (under JES3). In addition, all MVS and JES messages of jobs to be controlled by the above facilities are tracked as well. All other messages are immediately passed back to MVS. When a relevant message is encountered, the following actions are performed:
CMEM checks whether the related job or event has been defined in a CMEM table. This search is performed in storage because the CMEM table is loaded into storage when CMEM is initialized.
If the job or event has not been defined in a CMEM table, CMEM passes the message back to MVS.
If a relevant event is encountered, the CMEM rule passes the FORCEJOB and RESOURCE requests to the Control‑M monitor, which performs the requests. The STOPJOB and CONDITION requests are performed by the CMEM monitor.
All CMEM activities (except the last item above) are performed in storage. No I/O or supervisor calls are required. Therefore, no special tuning activities have to be performed and there is no reason to monitor CMEM performance.
Control‑M monitor overhead can easily be monitored by any locally employed performance tool.
