Tuesday, December 13, 2016

Hercules/MVS Turnkey - MVS on a PC

I started my career as an operations analyst. Worked my way up to be a systems programmer for MVS. During my career as a systems programmer, I wrote several assembler programs on MVS. Those were interesting days and nights.

I was actually surprised to know that I can install MVS on my PC. The same version of MVS I supported - MVS 3.8! I know, it's not state of the art. It's just 24 bit addressing! But I think it is a good tool if one wishes to learn about operating systems in general and MVS in particular. Or if one just wants to relive old glory days in writing assembler code.

What is MVS Turnkey?
MVS Turnkey is a port of MVS 3.8 to the PC. It runs under Hercules, which is a software that emulates various IBM mainframes. You basically install this on your system and then install MVS 3.8 on top of it. You can download the MVS Turnkey CD ISO image.

You can download it and run it on Windows or Linux. For Windows, you need Cygwin to run it.

Initial Impressions
After installing it, I was surprised to see the familiar MVS IPL screen. After the IPL, I tried running a dummy IEFBR14 job and it ran. The output was actually displayed on another window.

Next I was a little bolder. I ran an IEHLIST. Again, I was delighted to see the output.

The next step was a big test. I ran a simple assembler program. Nothing big, just to test if the assembly, link and go will work. And it did!!!

What surprised me most was how I was able to write the JCL and program on Linux and submit it to MVS.

Understandably, there is no ISPF, RACF, IMS, DB2 and other systems that make MVS useful. However, just by having an MVS system on a PC, someone interested in MVS can learn a lot of things like JCL, JES2, MVS initialization and customization, assembler programming which can lead you to becoming more intimate with MVS system areas. This is one of the reasons why you'd want to write an assembler program in the first place.

Documentation is available and it helped me recall how to IPL MVS and format JES2. It also provided a JCL and simple assembler code for the assemble/link/go job.

This looks very promising and I am looking forward to spending more time with my new found toy.

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