>In what way do they say PSA is a common area of every address space when >there is a unique PSA for every processor ?
"common area for every address space" has nothing to do with "processor". It says that no matter what address space you are in you can access fields in the PSA. And that is true. That is unlike "private area" where the private storage at address X in an address space has no necessary correlation to the private storage at address X in another address space. PSA is an MVS (probably older than that, actually) term. It has not to my knowledge ever varied from "prefixed save area". Within there you will also see "FLC" for "Fixed Low Core". Neither of these is an architectural term. As was mentioned, prefixing is a hardware function, provided so that programs could use the same address (e.g., 0) but get to a different area per processor. Many fields in the PSA are the same in every processor's PSA (e.g., the address of the CVT), but many are different (e.g, the address of the home TCB, the address of the home ASCB, the address of the LCCA). It is true that in between instructions (when not disabled for I/O and external interrupts) your work unit could be moved to another processor where it would then reference a different PSA. But for the most part the program is expected not to care -- for the things that the program needs, the PSA is expected to be "correct" on whichever processor the program is dispatched. When a work unit is undispatched from one processor and redispatched on another, about the only "normal" things updated in the PSA are the home TCB and home ASCB addresses. Another thing that is updated is the FRR stack. The FRR stack is saved upon undispatch and the "target PSA's" FRR stack is set up from that saved FRR stack to accompany the redispatch. There are some other things that are updated upon redispatch related to the status of the work unit; those are not used as frequently by applications. Peter Relson z/OS Core Technology Design ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
