Setting ARCH is like playing Blackjack or Twenty-one: guess too low and it is
sub-optimal; guess too high and you bust.
Note that everything we have said here about ARCH and TUNE applies equally to
COBOL as to C/C++. Of course if you are writing programs for in-house use your
universe of machines to support is much smaller. The classic error is
forgetting about your DR machine.
At CorreLog we managed to ship a C++ build to someone who was too back-level
for our ARCH. So George -- any of you who know George know that he is a good
guy but a yell-er -- yelled at me that the S0C1 was totally unacceptable -- we
needed an error message. I pointed out that SYSTEM COMPLETION CODE=0C1 *is* an
error message, but he was not having that. So I wrote some assembler code and
C++ to compare the compiled ARCH level -- you can retrieve it with __ARCH__ --
and put out our own message if there were a conflict. Obviously you need to do
that just as early in your run process as possible or the train will have
already left the station and run into a wall.
Here's an exercise for the readers. If you want to insert some code into a C++
module such that it will run just as early as possible during the run
processing, where do you put it and what else do you do? (Hint: "right after
int main(int argc, char* argv[]) and cross your fingers" are NOT the right
answers.)
Charles
-----Original Message-----
From: IBM Mainframe Discussion List [mailto:[email protected]] On Behalf
Of Charles Mills
Sent: Tuesday, April 25, 2023 7:06 AM
To: [email protected]
Subject: Re: XLC architecture level question
ARCH level is a "problem" I have dealt with for 12 or so years.
I say "problem" in quotes because it is not much of a problem -- you only have
to revisit it once every two years, and even then it is not an urgent problem.
So you don't need a solution that runs on autopilot -- you can just revisit
your decision every two years or so.
You need a management policy. The one I have advocated to my management is "we
will support the oldest hardware supported by the oldest supported release of
z/OS." I point out that while there may be lots of customers out there running
z9's, they probably are not buying a whole lot of OEM products. Currently that
would be ARCH(10), representing the zB/EC12, supported by z/OS V2R4. Once V2R4
goes out of service it would become
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