PH04166: ABEND0C4 DSNLXCMT+2F8 AND DB2 CRASHING WITH 04E 00D94001 AFTER AREORG DISCARD UTILITY HAS RUN 18/10/30 PTF PECHANGE

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• Applications got an abend0C4 in DSNLXCMT +02f8 and DB2 crashed
  with abend04E RC00D94001 .
  Subsequent analysis showed a 1-bit overlay in a control block
  (QRDA) caused by a REORG utility with DISCARD option that had
  run to successful completion a few moments earlier.
  Additional investigation concluded the following scenarios
  are exposed to this:
  1-REORG DISCARD is run and performs table space type conversion
   from single table linear or non-UTS segmented table space to
   PBG.
  2- REORG DISCARD on non-partitioned tablespace (with or without
   pending alters or extended page conversion) and the ptf for
   apar PI85843 is applied on subsystem. This apar further
   exploited a base code bug that has been there since Db2 V10.
  

Local fix

• Removing the PTF of PI85843 will highly diminish the chance for
  the problem to occur, but the error will completely disappear by
  avoiding DISCARD in REORG until a fix can be provided.
  

Problem summary

• ****************************************************************
  * USERS AFFECTED: All Db2 11 for z/OS users of REORG           *
  *                 TABLESPACE utility performing table space    *
  *                 type conversion to PBG or running on non-    *
  *                 partitioned table space with APAR PI85843    *
  *                 PTF UI56994 applied.                         *
  ****************************************************************
  * PROBLEM DESCRIPTION: With APAR PI85843 / PTF UI56994 applied *
  *                      or when performing table space type     *
  *                      conversion to PBG, a REORG TABLESPACE   *
  *                      DISCARD on a non-partitioned table      *
  *                      space resulted in a one bit storage     *
  *                      overlay in above the bar storage.       *
  ****************************************************************
  * RECOMMENDATION: Apply corrective PTF when available          *
  ****************************************************************
  User ran a REORG TABLESPACE DISCARD on a non-partitioned table
  space, which executed and completed successfully.  Then a short
  while later, Db2 abnormally terminated with ABEND0C4 DSNLXCMT +
  x'02F8' and ABEND04E 00D94001 due to a 1-bit storage overlay on
  an internal control structure in above the bar storage.
  
  The reported problem is caused by REORG DISCARD execution which
  overlaid one bit of storage in above the bar address when data
  is being discarded.  This can happen in one of two scenarios:
  
  (1) User is performing a table space type conversion from a
      non-partitioned table space to PBG via the REORG TABLESPACE
      SHRLEVEL REFERENCE or CHANGE utility running with the
      DISCARD option
  
  (2) After applying APAR PI85843 / PTF UI56994, REORG TABLESPACE
      DISCARD is run on a non-partitioned table space.
  
  Note that due to the random nature of the one-bit storage
  overlay, varying symptoms could have occurred as a result.
  
  Additional keywords:  ABENDS0C4 OFFSET02F8 SMCOVERLAY
  

Problem conclusion

• Code has been modified to prevent the aforementioned storage
  overlay during REORG DISCARD execution.
  

Temporary fix

• *********
  * HIPER *
  *********
  

Comments

APAR Information

• APAR is sysrouted FROM one or more of the following:

• APAR is sysrouted TO one or more of the following:

  UI60339

Modules/Macros

•    DSNURFBR DSNURFIT DSNURSCN
  

Fix information

• Fixed component name

  DB2 OS/390 & Z/

• Fixed component ID

  5740XYR00

Applicable component levels

• RB10 PSY UI60339

     UP19/01/03 P F901 «

Fix is available

• Select the PTF appropriate for your component level. You will be required to sign in. Distribution on physical media is not available in all countries.