Hi Derek,
Out-of-the-box, UMON attempts to track MVS program management events. Some software components such as IMS and CICS like to perform their own program management. IMS likes to mock up its own MVS program management control blocks in a way that was pretty good in the 1980s but is not completely how z/OS does it now, so that creates pain of its own. CICS likes to present as an opaque black box, so the OS has very little idea of what's going on inside. Fortunately (?), program fetch has become more sophisticated since the days of 370 load modules, and so not even CICS tries to perform its own program fetching anymore. Both IMS and CICS perform directed LOADs where they tell the OS which storage to load the module into. After that, the OS does not track it, but UMON can record the LOAD event for these programs as usage most of the time.
The usage for CICS application programs collected by UMON for uncustomized CICS regions reflects the activity required for CICS to load the program into the CICS region. Use of said program, and indeed the presence or absence of said program cannot be detected by the OS and therefore cannot be detected by UMON. When a CICS region is customized by installing the UMON CICS GLUEs, it becomes possible to record the use of programs within CICS regions. However, we all know that since CICS is so efficient, any attempt to monitor what's going on inside a CICS region will immediately add to transaction overhead, most likely in a noticeable way. Still, some customers really like tracking CICS program usage so much that they are willing to put up with some pain in that area.
My recommendation is to NOT activate UMON CICS program monitoring in unless there are clear benefits. You may want to try it in test/development systems to assist in seeing how the application performs some transactions, and you may even want to do it in production for short periods of time to get some usage statistics for discussion and analysis purposes, but activating it for all production regions all the time is what I'd call a "courageous decision". Of course, if you have spare capacity on the system then maybe it can handle a bit more overhead – YMMV.
If using it, see if the HSIZFTCn GLUE is sufficient for your needs. Sometimes it isn't, such as when trying to track dynamic LINKs by COBOL programs, for which you need to install the HSIZEIIn GLUE as well.
If you're using it and CICS overhead suddenly becomes unacceptable, remember that the UMON CIC(N) setting can be set dynamically to disable all UMON CICS GLUE data collection on a system-wide basis.
Regards,
Greg
IZSAM punched card DEV/L3
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Original Message:
Sent: 7/17/2023 4:50:00 PM
From: DEREK POWE
Subject: Product Usage Question
We found a situation where product usage shows some discrepancy between batch or TSO user interaction and CICS interaction. We see situations where a product may show 3 CICS region interactions over the course of a month but we know that users or batch jobs access the product several hundred times under the CICS region. However, this isn't shown when looking at IZSAM's product usage report.
Is that a known limitation where the access of a product under CICS isn't able to be shown? Or while a CICS region has a product "open" it can't determine if it's being called multiple times?
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DEREK POWE
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