February 17, 2020

[Exploring Mainframe] IBM System/370, MVS on Hercules Emulator

Only time I used mainframe (https://en.wikipedia.org/wiki/Mainframe_computer) was in college many years ago.  I took Cobol course on VAX (https://en.wikipedia.org/wiki/VAX) as it is still widely used at government and financial institutions.

Since then I've been working on all types of "the latest" technologies.  Always new, shiny stuff, never any "old" technology.

Now this new group I'm working in -- they use mainframe heavily.  I don't have to use it directly related to the work I have to do, but data I use comes from there. From reading some articles on IBM mainframe -- H/W, OS and its capability and features, I found it's quite interesting.  The terminal is still 3270, but the H/W and OS are pretty advanced.

I don't want to mess with work mainframe as it's a mission critical system.  Finally found some good emulator -- and this video shows how to install the emulator.  Although this one shows old (80's) system but it's a good tool to learn how things work and the terminology.  I'm going to try installing z/OS some time.

The video is quite long, but he shows step-by-step how to install and use it.

Some folks told me "it's a waste of time learning mainframe."  I'm planning to learn it enough to use it to be able to retrieve data/information.  Besides, mainframe is new to me.

Youtube URL= https://www.youtube.com/watch?v=QTxe8ASdxE0

Some pointers



  1. Unzip tk4-_v1.00_current.zip into folder MVS3.8
    e.g.) C:\opt\mainframe\MVS3.8
  2. Add the installation path to PATH environment
    e.g.) C:\opt\mainframe\MVS3.8\hercules\windows\64 (or your Hercules install directory.)
  3. open C:\opt\mainframe\MVS3.8\conf\tk4-c.cnf (this is main config file), increase number of CPU
  4. open cmd, go to C:\opt\mainframe\MVS3.8\unattended
    > set_console_mode.bat  (one time step)
    > cd ..
    > mvs

    (use 'esc' to switch view) 
After running mvs, try following in Hercules emulator
To get time
herc =====> /d t

To display all active jobs
herc =====> /d a,l

Connect via terminal

  1. Using wc3270, set up to connect to "", port "3270".  If you use "localhost", it tries to connect to IPv6, and won't connect.
  2. Screen will clear, and you'll see "INPUT NOT RECOGNIZED"
    Type "herc01"<ENTER>
    It'll ask for password.  Type "CUL8TR" (it's in the PDF manual) <ENTER>
  3. press <ENTER> again.
Watch the video and read the PDF manual.


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