Tom:
Well, actually I did write some privileged code. I believe that my code
contained the only (if not one of the very few) PTLB (Purge Translate
Lookaside Buffer) instructions in MVS.
I had (may still have?) a fair amount of code in the nucleus in the
Virtual and Real Storage Manager components (quickcell and paging
services).
I thought there was some version of DFP where they finally removed the
ISAM compatibility code, but I don't remember any official declaration
of that, just that the use of ISAM phased out on its own after the
introduction of VSAM in MVS.
ISAM did some pretty interesting channel programming. It was back in the
late '60s and early '70s while teaching the internals of ISAM and BDAM
to Program Support Reps that I learned about self-modifying channel
programs (fun stuff).
Mike
Tom Marchant wrote:
On Thu, 17 Dec 2009 16:27:10 -0500, Mike Myers wrote:
Yes, I had forgotten about SIO/HIO/TIO and was reminded of those by your
first post. I can't recall if I ever personally wrote a SIO instruction.
Most of the channel programming I ever did was at the EXCP level, so i
don't recall writing a SSCH instruction either.
SIO was a privileged instruction, so you wouldn't have done that unless you
were running in supervisor state. Same with SSCH.
As for the ISAM compatibility interface in VSAM, I think that went out
around the same time as ICF catalogs came along.
No. Not even close. IIRC, you could even use actual ISAM until 2000. ICF
catalogs were out long before 1990. Support for ISAM applications is still
in VSAM. I've never heard any statement that it will be withdrawn.
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