On 06/08/2017 11:45 AM, John McKown wrote:
This still seems to be supported in z/OS 2.2. Does anyone need to run a
program V=R in today's world? I'm just curious because this support seems
to be a "waste" of protect keys 10 through 15. Of course, if those keys
were "freed up", what could they be used for?
IBM Prolog for 370 (MVS) used them and it was a V=V program product.
It had originally used Key9, but CICS pushed the development
group and it got changed. Seemed that when Prolog was run in a
CICS space it caused CICS problems by making a page here and
there key9.
The keys were set to assist the engine in determining when a heap
or stack was about to overflow. For either one, the first time it
PIC4ed it was noted that garbage collection had to be done. If it
fell back below the "warning" page, the flag was reset. If it got
up to and hit the second page, then it began cleanup and shutdown
due to lack of memory for heap or stack, which ever it was that
had run out of room.
All of this was done to make it run as much as possible like it
had under VM. As a result, IBM's Prolog on the MVS platform was
much faster than any competitors (or so I was told in those days).
That is as much as I can remember. I wrote the CHANGKEY code,
cross-memory charge back SMF record, and SVC for it back in 1991.
I haven't seen any of it since.
Regards,
Steve Thompson
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