Mainframe, MVS and zOS Discussion

Hello -

My name is Bruce Yelen and I've been involved with mainframes since 1975 (yeah, I'm an "old-timer"). I "stumbled" across the forum while searching for a new position, and decided that participating will be a great way to determine what others are doing.

For many years my focus has been CICS, both as an applications and a systems programmer. For the last 15 years I've been writing middleware that allows client applications using Sybase database servers on Windows and Unix/Linux systems to make RPC calls and language requests to the mainframe (via CICS) that looks to the client as just another database server. I also support an api that allows CICS applications written in COBOL/PLI/HLASM to return data in response to these RPC calls. This involves some very heavy "down and dirty" use of socket interfaces, exits, and so forth to accomplish. I'd say 70% of our code is assembler, with the other 30% being written in "C". Our only use of COBOL is for example code that we provide our customers.

In the "Ancient History" department, I started with the very earliest versions of the operating system we now know as z/OS. If I haven't left anything out, the progression went something like this: OS360/MFT -> OS360/MVT -> OS/VS2 -> MVS/XA -> MVS/ESA -> OS390 -> z/OS. MFT and MVT stood for "Multi Processing with a Finite number of Partitions" and "Multi Processing with a Variable number of Partitions". With MFT, you could only run as many jobs as partitions, and each partition was hard-coded into the sysgen with a specific amount of storage available. MVT did not use partitions, but you could not exceed your total amount of memory. OS/VS2 was the first in the series that supported the new virtual memory features of the old IBM System/370 line.

I've also worked with ACP (Airline Control Program) which was a forerunner of today's TPF. It's been an interesting ride and just gets better!

- Bruce

Hello Bruce,

Welcome On-Board and Thanks for introducing yourself - it's nice to know each other!

Ah...I don't really feel that someone is an old-timer ever - may be 'experience-timer' is a better word... . When I think about the time back when Internet was not that common I usually start thinking how much time the people must have spend with manuals, without "ctrl+F" that must have been tough!

Said that, I look forward to your contribution to this Board and you too will find this Board Helpful and Enriching as we go along.

By the way - was it through a google search when you found us?

Stay around and have a good one,

Hi Anuj,

Yes, I found the site through Google, their web crawlers have found you (GRIN!)

I really don't feel like an "old-timer" unless I start reflecting on things, an example being that the laptop I'm writing this post on has more memory and a lot more computing power than the first mainframes I ever worked on, an IBM 360/165 and an IBM 370/168. These two machines (and assorted control units, tape drives, disk drives, printers, etc.) took up an entire room running about 5000 square feet! Aside from being on a raised floor, with cooling running underneath, the 370 also water cooled. It required it's own special cooling unit located in a separate facilities building!

- Bruce

I never liked crawlers and spiders this much ever before until I created a website!

With current land-rates in "a good a locality" in Mumbai, India - the land for those two machines would just cost Rs. 250,000,000!

On the other hand, what's your take on that - why did IBM invest separately in ACP/TPF back then when System/360 was available already? My practical experience with TPF is pretty less but what I read is that - this operating system is a special-purpose system that is used by companies (mostly airlines) with very high transaction volume ...but I've worked with large to very large banks and they used zOS mostly - so airlines could have been handled on s/360 itself, no?

On the other hand, what's your take on that - why did IBM invest separately in ACP/TPF back then when System/360 was available already? My practical experience with TPF is pretty less but what I read is that - this operating system is a special-purpose system that is used by companies (mostly airlines) with very high transaction volume ...but I've worked with large to very large banks and they used zOS mostly - so airlines could have been handled on s/360 itself, no?

ACP was an operating system. It devoted the entire resources of the hardware it was running on to transactions. Originally designed by IBM and American Air Lines (the original SABRE system), it was also picked up by some large hotel chains and a couple of loan companies. Since the entire system was given over to running transactions, a separate mainframe was required (running MVT/MVS, etc.) to do compiles and prepare program loads. There was a batch simulator that would run under mvs to allow a limited amount of testing. Otherwise program testing had to be run on an ACP system. When I was working at Eastern Air Lines in the 1970's, we had a 370/195 running MVT, a 370/195 running ACP, and a 370/148 running an early form os OS/VM. That was able to support 3 small vm's running ACP for testing purposes.