Customize MVS logon screen

Getting a little bored with the standard MVS logon screen? Here you can find a recipe to change the screen to your own liking.


You have to dive into SYS2.CNTL and find member TK4-LOGO. That’s where the logo is stored. This is an assembly job that re-assembles the module for the logon screen.

Get rid of the old logo

Now first, find a line that says:


You are welcome trying to change the lines before this, and this one, I decided to leave stuff intact up to and including this line. Then, you can find other lines that reads:

         $SBA  (17,12)
DC 'TK3 created by .... etc

I left this intact as well (for now). I did comment out the old lines, by putting an asterisk in column 1 in every line in between the two I mentioned above.

Create your own logo

There is a little Linux script to convert ASCII text to the assembly statements you need. See below.

#Mihai Criveti: generate LOGIN splash for MVS
#Usage: ./ dino > out
for line in $(cat ${logo})
  echo "         \$SBA   (${linum},15)\n"
  echo "         DC     C'$line'\n"
  echo "         \$SF    (SKIP,HI)\n"

What I did in between is create my own logo and text, as you can see in the screenshot below:

Every line on the logon screen has three lines in this assembler program. The first one reads:

        $SF (SKIP)

The (SKIP) will result in normal text for the next line (blue on my screen), whereas (SKIP,HI) will yield highlighted text (white of my screen). There’s probably more of these attributes, feel free to let me know in the comments if you find them?

The second line of the group of three is a line that reads:

         $SBA   (row,column)

This takes care of positioning your text on the screen.

Then the third line of the three is your actual text, it reads:

         DC     C'Some text that you want on your logon screen'


When you think everything is okay, save your data and submit this job. Check it in the output queue; all steps must have ended in RC=0000.

Now activate it

To make the new logon screen active we have to shut down VTAM and bring it back up. Mind you, TSO will be shut down in this process, so save your work, and logoff from TSO. The commands below can be given from the http console.

The way I did it is described below, I use console commands, perhaps you need to precede them with a slash when you’re not on an actual console. Furthermore, there’s probably more ways to do it, but this worked for me:


Those last two programs are not stopped by the Z NET,QUICK command, so we have to terminate the ourselves. When all dust has settled down and SNASOL and JRP are stopped, we can bring all of them back up again:


Now we can connect a terminal. In my case it showed the old logo at first, without a logon prompt. That’s probably something that Hercules shows us. But when I pressed enter, there it was, my new logon screen:

My new logon screen

Logon screen considerations by René Ferland:

The logon screen is presented to us by VTAM. Professor René Ferland found out the following for me:

For VTAM connections, the logo is produced by the network sollicitor SYS1.VTAMLIB(ISTNSC00). From what I know, ISTNSC00 just expands the assembler macro SYS1.UMODMAC(NETSOL) which itself includes the copy book SYS1.UMODMAC(TK4MLOG) containing the TK4- logo. So, to change the logo, you need to change SYS1.UMODMAC(TK4MLOG), re-assemble, re- link ISTNSC00, store the module in SYS1.VTAMLIB, and restart VTAM. I don’t know which job assembles and links ISTNSC00 for TK4- using the macros in SYS1.UMODMAC (instead of the standard NETSOL macro in SYS1.MACLIB). Tommy Sprinkle web site has an job example for ISTNSC00. You can try that but backup your system before. :smiley:

After a while, he also wrote:

I found the job to change the logo: SYS2.CNTL(TK4-LOGO). Now, you may customize your cloud system. :smiley:

I found out one only needs the last job, SYS2.CNTL(TK4-LOGO).

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