Question & Answer
Question
We run three copies of our scheduling system. Each copy has its own hook on IEFACTRT. Two of the copies run at MED_STC, and one runs at SYSSTC. I'm wondering if it is plausible that an explanation for my relatively high uncaptured CPU when multiple jobs end, is because I must pass through all three of these exits each time a job ends. I'm also wondering if the three exits slow down my lpar when the system gets very busy because two of the three exits might take run at MED_STC, or do the exits run at the dispatching priority of the job that ended ?
Answer
IEFACTRT exit runs under the initiator TCB. This time is uncaptured for the SMF 72.3 but will be included in the SMF30 initiator time.
You can check overall SMF30 initiator time fields:
SMF30ICU (INIT CPU time under TCB)
SMF30ISB (INIT CPU time under SRB)
You can sum SMF30ICU and SMF30ISB for all jobs and see if that tends to increase for the times that the overall system uncaptured time increases. You can also see how much of the overall system uncaptured time it accounts for.
IEFACTRT will run at the initiator dispatch priority which is by default FE (equivalent to SYSSTC dispatch priority) but can by different if you use the INITIMP parameter in IEAOPTxx parmlib member.
If this code takes a lot of CPU and runs at the high FE dispatch priority then yes that can impact the rest of the system.
The general recommendation is to use the default for INITIMP. This will mean initiators start the next job in a timely manner. If the CPU time consumed by the initiator processing is high enough to cause an impact to the rest of the system then you may need to use INITIMP to decrease the dispatch priority. The drawback is that the INIT processing itself may slow down which is may slowdown the starting of the next job.
From your update above it sounds like some of your scheduler tool runs in MED_STC.
The actual IEFACTRT exit will run as per above.
If it somehow triggers something in your scheduler tool then the scheduler tool address space will run at its own dispatch priority and that time is likely captured in your scheduler tool srvclass.
Historical Number
26976;227;000
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Document Information
Modified date:
03 September 2021
UID
isg3T1020784