++ USERMOD(TX67893)     /* REWORK(20210408) */             .
++ VER (X067)
   FMID(EDM1101)                                           .
++ IF FMID(EPM1101) THEN REQ (UX15738)
 /*
   PROBLEM DESCRIPTION(S):
     TX67893 -
       Abend in VS1 6.7 display console initialization during NIP.

       When VS1 6.7 attempts to activate consoles at the end of
       NIP, activation of display consoles fails, probably due to
       a race condition in which fields that are expected to be
       initialized haven't been initialized yet.  DIDOCS display
       console activation issues an OPEN for a DCB pointing to a
       DD statement constructed to define the console device.
       OPEN module IFG0196X issues a QMGRIO macro to write back
       the possibly-modified JFCB for the device being opened.  In
       the course of the QMGRIO, one of the following generally
       occurs:

       (1)  The QMGRIO macro expands to instructions to obtain
            the address of the QMGRIO service routine by chaining
            through the CVT and JESCT, then doing a BALR to the
            address obtained.  The CVT pointer to the JESCT,
            CVTJESCT, is zero, causing what the macro believes to
            be the address of QMGRIO to be garbage, so the BALR
            results in an abend0C1; or

       (2)  CVTJESCT has been initialized correctly, so the QMGRIO
            service routine receives control as it should, but its
            validation of the QMGRIO parameter list passed by
            IFG0196X finds the parameter list is defective, with
            fields that should be initialized set to zero, so it
            issues an abend1B0.

       After the abend, initialization of the display console
       stops, but its UCM is marked active, so messages are queued
       to it.  Because those messages are never displayed, WTO
       buffers are eventually exhausted.

       IFG0196X is changed to bypass the QMGRIO if the current
       task is the communications task.  This is a circumvention,
       not a fix, but it allows console initialization to complete
       successfully.

       Note that this usermod assumes that the fix for UX15738
       has been installed on the current system.  UX15738 fixes
       a problem with linkage editor EXPAND processing in the case
       of a target load library that has a block size that is a
       multiple of 1024 (the EXPAND appears to work, but
       patterns of binary zeroes are written over the first few
       bytes of the module).  Another problem encountered during
       the development of the usermod was the fact that IBM linked
       IFG0196X as NE (not editable), so the module has no ESD and
       cannot be reprocessed by the linkage editor.  That problem
       was circumvented by reconstructing the module in SYS1.AOSD0
       prior to VS1 system generation using the DELINK0 FE aid.

       Also note that TX67893 checks to see if the current job
       is the communications task by checking the TIOT pointed
       to by the current task for job name "CONSOLE", step name
       "SYSTEM", procedure step name "VMS".   Don't use that
       job and step name combination for any ordinary VS1 job,
       or it will be treated as the communications task and the
       QMGRIO bypassed.

   COMPONENT:  5741-SC1D1-EDM1101

   APARS FIXED: TX67893

   SPECIAL CONDITIONS:
     DEPENDENCY:  IFG0196X in the target SYS1.SVCLIB must
      already have been relinked to remove the NE (not
      editable) attribute set by default in the standard
      IBM distribution.

   COMMENTS:
     LAST CHANGE:  2021/04/08

     REWORK HISTORY:
      2021/04/08: Created.

     CROSS REFERENCE-MODULE/MACRO NAMES TO APARS
      IFG0196X  TX67893

     CROSS REFERENCE-APARS TO MODULE/MACRO NAMES
      TX67893   IFG0196X

     THE FOLLOWING MODULES AND/OR MACROS ARE AFFECTED BY THIS USERMOD:

     MODULES
       IFG0196X

     LISTEND
 */.
++ ZAP      (IFG0196X) DISTLIB(AOSD0   ).