Monthly Archives: July 2012

=3.4 or the most important mainframe command

Once you are on a mainframe, the most important command is: =3.4. This command is issued on the command line of the so-called ISPF screens.



If you are in this screen, simply issue =3.4 and you are in the screen that gives you access to all files. This is the stepping stone into the work that you might create: it gives you access to output, input, jobs and everything else that is important in your mainframe life.

There is a second command that is of equal importance: the PF3 command (for some reason, the IBM mainframe boys and girls use PF3 for the F3 function key). This means: go one step back. Repeatedly tapping the F3 key leads to the exit: the end of a session. I noticed that the PF3 command is also labeled as “End”. This means that if you read : “enter end command to return to the primary option menu” should be interpreted as press F3 to return. Do do tap on the end key: it does not give you the desired result. No use the F3 key. Hum, a fact of life.

I would place a bet that you are able to do a simple session on a mainframe with just these two commands: the =3.4 and the PF3 command. If I was to write a quick guide for a mainframe, I would start with these two commands.

Going back in time – or re-enter the mainframe

When I entered the world of the mainframe, I realised that this is a world on it own; it has their own rules and newbies are not easily accepted here. From a support form I read this message from a sysadm: “.. (this) is a system for people who know what to do and how to do it. It is not a system for obvious clueless newbies like you. I suggest you start reading manuals for the next few weeks.
You are telling us “But I fail.”
Fail with what, failing to read manuals? Failing to tell us what error messages you get?”.
Ouch that hurts and it does not help the poor user who gets an error and doesn’t know what to do.

From the same forum : “Open a book on JCL – they are all available online and start reading about the required format…
.. further notes:
To other members: Do not provide “xxxx” with a solution, let him figure out what is wrong by opening a manual”.
Another example of the helpful sysadm. Another example of a user who is left in the dark.

This is the mainframe.

Compare these type of reactions to the gentle reactions on the Ubuntu site. It starts with: “You can find support from a variety of sources. Take a look – you’re likely to find an answer to every question. If you can’t find an answer, just ask the people in our active forums.”

The mainframe is completely different. A quick guide is nowhere to find; the manual are difficult to understand; the sysadm seriously believe that they are next to God.

However, I strongly believe that mainframe is less difficult than one might think. After all, it is created by ordinary people and their work should be understandable by us humble beings. I give first three books that may help you out:

  • Menendez & Lowe “Murach’s  OS/390 and z/os JCL”
  • Murach, Prince & Menendez “Murach’s mainframe COBOL”
  • Garvin & Eckols “Db2 for the COBOL programmer”

I will return with some elements that helped me understanding the mainframe.