[geeks] On the subject of mainframes...

[vintagecoder at aol.com]

md.benson at gmail.com wrote on Sat May 28 18:00:49 2011:

> Hi,
>
> I have got back to playing with Hercules and OS/360 on my Mac Pro.

Excellent!

> Got it up and running using a pre-packaged OS/360 CD bundle from
> somewhere. I followed the included instructions and it seems to fire up
> okay and I can run up MVT. I dunno if that's enoigh to work with or if I
> need something else on top...

MVS (and this is a name that applies generally to OS/360 up to the current
day z/OS) has always been about getting work into and out of the system as
fast and safely as possible. In the early days and for a long time after,
that input came from decks of cards and open reel tapes. It wasn't an
interactive system by any means and today looking back it's sometimes hard
to understand how we got anything done back then, but we did and we had a
lot of fun.

MVT was a great OS but if you never used it you're going to want to commit
a lot of time to getting something out of it. I'll compare getting a
running MVT system with doing a minimal NetBSD install. Well, it's way
harder but they've already done the sysgen for you. After that, all you have
is a basis for building a system you really want. You have an assembler,
a few languages, and ways to get work in and out of the system, but not a
whole heck of a lot more than that. Now you have to start writing your
tools and building what you want.

It was actually easier using it back in the old days when we had keypunches
and card readers and operators to hand us our printouts. Since there was no
online editor for another decade or so you will need to learn some
utilities or even the fact you have a modern keyboard and editor running on
OS X won't help that much. You will be able to submit jobs and get output,
but not do much else, without learning the utilities. MVT is not really a
practical system for learning on after all these years, it's just too much
work unless you really like hurting yourself. I don't know what you got on
that bundle but most of the packages I have seen for OS/360 have the
original compilers which should include FORTRAN (roughly equivalent to
FORTRAN IV/66), PL/I, RPG, and COBOL. You will also have a copy of Assembler
F (IFOX00) which is a great way to get started learning MVS assembler, books
are available for virtually everything on bitsavers. If you have JCL to run
compiles and links you will be able to submit programs, compile and link
them, and get the output. You will need to learn basic operator commands
to deal with starting and stopping printers, bringing tapes and disk
drives online, etc. and cancelling runaway jobs if you make a mistake
coding. You will need to set up some stuff to do that and so you will need
to learn to use the utilities. The utility programs do things like set up
procedure libraries, allocate and manage load libraries (executables),
edit library members, and process input and output. All your actual
program editing will be done on your host platform and you will submit the
jobs through the virtual reader in Hercules to your system. But that's the
only easy part.

>
> I'd like to do something with it but I basically don't have a damed clue.
> I have a bundle of documentation on OS/370 but I don't have OS/370. 

The Turnkey MVS 3.8J (which ran on S/370) might be better for a few
reasons. One, you have TSO which is a way to communicate with the terminal.
It is very primitive at that level and you will have only a line editor and
some commands. I used line editors on PDP machines in the 1970s so nobody
start with me about interactive systems, and here we are talking about a
system that came out in 1974. Later they added ISPF which is an actual
workable editing and job submission environment with a full screen editor
and tools for doing a lot of things that we use currently, but it was not
released to the public domain and is not available anywhere I know of
outside of IBM customers. So you can either learn the old TSO, or
utilities, or you can use an add-on product called RPF that is available on
the Turnkey System. It gives you an ISPF-alike system to make editing,
browsing data sets, and reviewing your output easier. The single most
useful page I have found for running old MVS is here:
http://www.jaymoseley.com/hercules/

It has almost everything you need including tons of addons and updates.

> As a (relatively) young pup who never had access to a mainframe or time
> sharing systems I've no knowledge or experience of anything like this. My
> grounding is in NetBSD, Linux and desktop OSs. Is there anyone out there
> who'dbe willing to point me to some info or teach me some basics? 

I started back in the OS/MFT days and I fell in love with the environment
and have continued with it all my career. But it's really hard to learn all
that stuff now, years later because the way we all approach technology is
not like it was then. BTW, mainframes are still going strong. They're
everywhere, you might not see them or hear about them, but all the biggest
companies run them, and have to. Anyway, it's going to be a long hard
uphill battle and as much as I hate to say it, it might not be worth it for
you. If you are stubborn, smart, have plenty of time and desire, you can
definitely learn a ton of interesting stuff, some of it even useful today,
and mostly have a lot of fun. It's not just history, the great thing about
IBM hardware and OS is everything is backward compatible and everything
builds on everything else. You don't have to throw out what you know every
3 or 5 or twenty years. You just keep building on what you know which is
why the people who worked up in that environment like it so much. You
can take 35 year old object code and it will run on today's biggest
systems. The documentation is superb and code quality is outstanding. Every
message from every IBM product from the OS to languages can be found in a
book. There aren't any "oops" or "sorry" messages, but standard prefixes
and a coherent numbering system that helps you get answers fast, after you
learn the system.

Enough cheerleading on my part, I would suggest a few things to get started.

First, get a yahoo id and join all the hercules 390 groups. There is one
for Hercules itself and there is one called Hercules MVS (I'm not sure of
the exact names) and another one that deals with the Turnkey MVS3.8J system.
The Turnkey system is a system genned by old time sysprogs and comes with
modern extras that make life simpler. Plus you will be on the same page
with other people who are using the turnkey distribution. I would suggest
you don't install anything further until you ask on those lists (the people
are extremely helpful, btw, you will never see a suggestion to RTFM, unlike
in the BSD world) because the Turnkey distribution hasn't been updated in a
long time but I believe somebody is publishing updates and you may be able
to pull down a version in much better shape. Follow the lists, ask
questions, and try stuff out. If you want to go through a sysgen and see
how a system was built in the old days you can use Jay's MVS 3.8 procedures
described on the page I linked above. If not, get somebody to tell you
where to download the latest turnkey.

> 
> Also when we looked at this as a list someone recommended an excellent
> 3270 terminal emulator for OS X that was compile from source. I have
> tn3270 but it's a somewhat clunky Carbon port from OS Classic and it's...
> not optimal even though it's pretty good (as far as I can tell anyway). 

I don't know what they recommended, but many of us use x3270 (I use it for
work, it's stone reliable) which is a modern emulator from IBM that was
released. As far as I know it's actively maintained, I had no problems
getting hold of the maintainer last few times I tried. And it is in the
NetBSD pkgsrc tree.

It's been a long time since I used MVT very much and I will be glad to
answer questions if I can, but the guys using it every day for a hobby are
going to be a lot more helpful. Join the yahoo groups and have fun!

I am answering you on the list because I prefer not to communicate with
gmail accounts so I apologize to the list members since this long post is
probably off-topic. I'm hoping to get some Sun hardware soon which is why I
am on this list but since I work on IBM systems I couldn't help responding
to Mark's questions as well as I could.

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