I would suspect KSDS VSAM files that were being accessed randomly
without LSR processing. Use of LSR or conversion to sequential
processing is the suspected tweak.
Michael
At 09:06 AM 1/19/2025, Robert Prins wrote:
From LinkedIn:
<quote>
2 weeks ago I received the analysis data from a new client that wanted to
reduce their CPU consumption and improve their performance. They sent me
the statistical data from their z16 10 LPARS. Information about 89,000+
files. I analyzed their data and found 2,000+ files *that could be improved*
and would save CPU when improved. *I pulled out 1 file to demonstrate a
Proof of Concept (POC) for the client. I had the client run the POC and it
showed a 29% reduction in CPU every time that file will be used. The 29%
did not include 3 other major adjustments that would save an addition 14%
CPU and cut the I/O by 75%.* This is just 1 file. The other files can save
3% to 52% of their CPU every time they are used in BATCH or ONLINE.
</quote>
I've been a programmer on IBM since 1985, and the above doesn't make any
sense to me, how can changing just one file result in a 43% reduction in
CPU usage?
I've only ever been using PL/I, and using that I did manage to make some
improvements to code, including reducing the CPU usage of a CRC routine by
an even larger amount, 99.7% (Yes, ninety-nine-point-seven percent), but
that was because the old V2.3.0 PL/I Optimizing compiler was absolute shite
at handling unaligned bit-strings, but WTH can you change about a file to
get the above reduction in CPU?
Robert
--
Robert AH Prins
robert(a)prino(d)org
The hitchhiking grandfather <https://prino.neocities.org/index.html>
Some REXX code for use on z/OS
<https://prino.neocities.org/zOS/zOS-Tools.html>
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