> -----Original Message-----
> From: IBM Mainframe Discussion List On Behalf Of David Price
>
> What hardware are you on?
>
> I ask because a z196 has some high CPU costs for certain PSW Key-related
> instructions.
>
> For example, SPKA (Set PSW Key from Address) on a z196 shows up in CICS CPU
> figures because it stalls
> the pipeline when changing PSW keys between key 8 and key 9 -- or even when
> it doesn't change keys
> e.g. it is just 'going' from key 8 to key 8!
>
> SPKA may be executed in CICS more than you think (consider User Exits --
> GLUEs and TRUEs -- some of
> which may have been inserted by your monitoring software).
An interesting observation. I'd have thought that CICS (in particular), in an
early stage of startup when it runs authorized, would set the
"Storage-Protection-Override Control" (bit 39 of CR0) if STGPROT=YES was
specified as a DFHSIT parm. See z/Architecture Principles of Operation, 10th
Edition, at page 3-12 for details of "Storage-Protection-Override Control".
This would seem to obviate any need for CICS, post-initialization when running
unauthorized, to issue SPKA or similar key-related instructions.
-jc-
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