Re: CICS/400

I used to do CICS on mainframes some 35 years ago. When I was asked to
manage this thing in the corner of the computer room called S/38 ( no one
even knew how to power it on) and I figured it out, I never looked back. (I
had worked on the S/3 and it’s successors).

This is helping me remember why I left anything to do with mainframes. Too
much like work.



On Sat, Aug 12, 2023 at 12:57 PM Jon Paris <jon.paris@xxxxxxxxxxxxxx> wrote:

I don't think I can do much better than Mark's great explanation Jack.

The only thing I might mention is that the S/38 - IBM i paradigm of
interactive programming relies on an underlying OS feature - namely that
there is only ever one copy of the program instructions in memory and the
system always automagically handles _all_ of the memory for a user and
associates it with the program when needed. So state information (including
current file cursor positions etc.) is retained with _zero_ effort on the
part of the programmer.

S/34/36 MRT programmers had to actually decide which variables (including
of course current file positions) needed to be retained between messages
and on receipt of a new message they had to "page in" the appropriate set
of variables, reposition file cursors, etc. CICS is much the same except
that there is some built-in functionality to assist in the storage etc. of
state information. In both cases this programming had to be done without
the assistance of pinter-based dynamic memory - so making decisions about
which variables were to be retained was a major effort.


Jon P

On Aug 11, 2023, at 2:21 PM, Jack Woehr via MIDRANGE-L <

midrange-l@xxxxxxxxxxxxxxxxxx> wrote:

It might be interesting if you would expand on those remarks.

On Fri, Aug 11, 2023 at 12:19 PM Jon Paris <jon.paris@xxxxxxxxxxxxxx>

wrote:

For anyone who has ever done S/36 MRT programming CICS is pretty simple.

For those who grew up on the S/38 / AS/400 with the "why should I have

to

worry about state information?) mentality it is much harder. In some

ways

it is the same reason that programmers with that background have

difficulty

getting their heads around web programming. S/36 MRT programmers find

the

web a breeze!

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