To be clear, the CEX coprocessor and CPACF are different in some ways. ICSF operations run on the caller's unit of work, so they are subject to WLM (or whatever prioritization mechanism is used).
For CEX coprocessors, once the request is sent, ICSF suspends them since CEX requests are asynchronous. Contention for CEX is handled by FIFO. CPACF runs in lock-step with the CPU, so there isn't a concept of "contention" since CPACF operations ARE CPU instructions. There is a build-in model-dependent limit on how long a CPACF instruction can run before it self-interrupts. So, a better instruction to compare to would be MVCL. Eric Rossman --------------------------------- ICSF Security Architect z/OS Security --------------------------------- -----Original Message----- From: IBM Mainframe Discussion List <[email protected]> On Behalf Of Paul Gilmartin Sent: Sunday, February 8, 2026 1:13 PM To: [email protected] Subject: [EXTERNAL] Re: Is it safe to call ICSF service CSNBOWH in CICS? On Sun, 8 Feb 2026 03:33:03 +0000, Eric Rossman wrote: >It is safe. CSNBOWH only uses CPACF for SHA-1 (and SHA-2/SHA-3). > >For some of the other CSNBOWH rules, we do use software but none of the rules >use CEX coprocessors, which is why the service is not in the CICS WAITLIST >(CSFWTL01). Any service in CSFWTL01 could potentially get suspended so needs >to be off the QR task but CSFOWH (CSNBOWH) is not one of those services. How is contention for that coprocessor mediated? o FIFO (like ENQ)? o By dispatch priority of requestor? o Other? Is it affected by "nice"? <https://www.ibm.com/docs/en/zos/3.2.0?topic=descriptions-nice-run-command-different-priority > (I suspect similar considerations night apply to STCK.) -- gil ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
