Definitely not true on a system with multiple CPs: Even multiple TCBs in the same address space can have an active processor at the same time. Easy to observe on a CICS address space with heavy DB2 usage where processor utilization can substantially exceed 100% of one CP. A given TCB of course will at most have one CP assigned at any instant of time.
A running program can reliably ask what its own TCB is, but asking by any of several means whether other processors are associated with any other TCB, in your address space or another, gets an answer that is only correct at that exact different instant for each TCB and that may be wrong by the time you plan to use that information. By sampling you could perhaps get a statistical estimate of percentage of total CP usage by various TCBs (other than TCB of the sampling program, which will always be found active 100% of the time). There is no way to ask via program instructions about true concurrent CP usage. z/OS can measure CP usage by a TCB & Address Space to some extent by measurements at start and end of CP dispatching (captured CPU time). The Hardware can measure CP percentage active for each CP. Not 100% accurate but that's about as close as it gets. Joel C. Ewing On 5/16/21 9:25 AM, Joseph Reichman wrote: > At any nanosecond there is one > I guess if you had program running authorized and wanted to know where in > address space X the code is running or in the general vicinity once you got > the TCB then TCB->RB then looked at RBOPSW > > > >> On May 16, 2021, at 10:17 AM, Jeremy Nicoll <[email protected]> >> wrote: >> >> On Sun, 16 May 2021, at 14:54, Joseph Reichman wrote: >>> I was looking to find out in any given address space is there a way to know >>> what TCB is currently executing >> You're still wrongly assuming that there can only be one. >> >> Perhaps it would help if you explained why you need to know what is >> executing where? >> >> -- >> Jeremy Nicoll - my opinions are my own. >> -- Joel C. Ewing ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
