Emergency Removal of z/XDC From Your Running System

Occasionally, a customer may have severe problems with z/XDC, and he may want to revert to an older level of z/XDC. However, due to the design of z/XDC’s installation process, it is not possible to revert to an older level without either reIPL’ing or somehow clobbering z/XDC’s SSCT entry to make it not findable by z/XDC.

Typically, the easiest way to zap an SSCT on your running System was to use z/XDC to find it and zap it. But if z/XDC is not working correctly… Well, you can see the problem here.

To meet that need, we’ve written a standalone utility named XDCREMOV. Running it is simple. The JCL is:

  • //RESET EXEC PGM=XDCREMOV,PARM=XDC

What it does is, it finds z/XDC’s SSCT and changes the 4th character of its SSCTNAME field to a blank. This has the following effects:

  • For the currently installed System Interface, all of its elements become instantly disabled. This is because they have been coded:
    • To know where the SSCT is,
    • To know what the SSCT’s name should be,
    • To always check to see if the name has changed,
    • And to functionally NOP if the name has changed.
  • So changing the name of the SSCT completely turns off the existing System Interface.
  • Then the next time z/XDC is started authorized:
    • It will search for a previously installed System Interface and not be able to find it.
    • So it will install a new System Interface.
    • Since z/XDC cannot find its older SSCT, a level comparison cannot be done.
  • So a backlevel XDC will now install successfully.

In other words, once XDCREMOV has be run, you can now start up a backlevel of z/XDC with no problems.

To effectively remove z/XDC from your System, use the following process:

  1. Bring down z/XDC’s Server Task: C XDCSRVER
  2. Start a job that runs XDCREMOV authorized.
  3. Install the back level of z/XDC that you want to revert to.
  4. Restart the Server task: S XDCSRVER

Since XDCSRVER runs authorized, the replacement System Interface will be installed.

The XDCREMOV utility was added by update CBC-1809D. The starting point for more information is HELP WHATSNEW Z22 THINGSFIXED MAINTENANCE.

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