[geeks] On the subject of mainframes...

[Lionel Peterson]

Gear comments, just a quick note that there was an ISPF/SPF alternative that
ran on MVS, it relied on CICS and emulated ISPF/SPF - provided a very similar
interface with much lower overhead & cost.

As for a reason to go back? Aside from nostalgia, I agree there were precious
few programs that couldn't be run dramatically more efficiently under more
modern hardware/software...

A previous commenter wrote something to the effect of "I don't see how work
was done back then" - it was easy, once you got past the idea of working
interactively with a user. Writing basic mainframe batch code was like writing
a really, really big UNIX utility, where each program ran on either flat file
or database input, and generated either an updated text file(s) or database.
Using JCL 'glue' and utilities (again, similar in some ways to UNIX shell
tools) you'd string a bunch of single-purpose programs together to accomplish
a given task. Also, jobs could be scheduled for execution via JCL by working
with initiators (execution threads) that jobs could be released into, and then
the queued-up jobs would execute in a first-in, first-out manner.

Then there were interactive programs (CICS, TSO, IMS/DC were the big hitters),
writing them was different from batch programming, but not unlike web
programming now. The program would run, throw up a screen, and terminate. The
user enters data, hits an action key, and based on the key hit, the same or
another program would run, process the screen contents, update databases, and
then draw a new screen and end...

Mainframe tools were wonderful - and facilities like PDS (partitioned data
sets), VSAM files, and IMS/DB were great, and the JCL utilities were very,
very powerful, enabling one to accomplish a lot of work without writing any
code...

Ah, memories...

Lionel

On May 28, 2011, at 5:47 PM, gsm at mendelson.com wrote:

> I don't see any thing that a modern person would be interested in.