PI79178: 5C6-00C90F00 CAN OCCUR ON AN INDEXED QUEUE FOLLOWING THE BACKOUT OF AN MQGET.

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• ssid,ABN=5C6-00C90F00,U=STCUSER ,C=W9700.800.
  DMC-CSQIMGEF,M=CSQGFRCV,LOC=CSQILPLM.CSQIMGEF+00002E66
  .
  symptoms:
  .
  Jobname CICSxxx Conntype CICS ASID x00CA ASCE 1508B510
  EB 1437F6B8   ACE 1437F658  Thread 18E47490 Tran A001
    Task 0004236C
    TCB 008AAE88 Active in MQ
  EB latch held mask 00100000 (DMCNMSPC/XMCHASH)
     ***Abend and reason code  5C6-00C90F00
       -> CSQI_RECORD_DELETED
  .
  ACE(1437F658) +X'24' RAL(1436E990) +X'50'MTHR(5BB03040)
  +X'2C'MHPV +X'28'MHND
  MHND
  5BA4BE40 D41008D0 D4C8D5C4 00000001 00002002| M..}MHND........
  5BA4BE50 00002083 00000000 00000000 00010001| ...c............
        ----> MQGMO_FAIL_IF_QUIESCING,MQGMO_MARK_SKIP_BACKOUT,
              MQGMO_SYNCPOINT,MQGMO_WAIT
  5BA4BE60 5BB03040 81002000 10200220 02000000| $.. a...........
  5BA4BE70 00290000 5C557368 5C557368 5C557368| ....*...*...*...
  5BA4BE80 5C557368 00000000 00000000 00000000| *...............
  5BA4BE90 18E47514 00000000 00000000 1508B510| .U..............
  5BA4BEA0 00000080 7E846B24 5B9D0860 00000000| ....=d,.$..-....
  5BA4BEB0 D22D2126 C9A31E6A 00000000 D22D2126| K...It......K...
  .
  MQGMO_* (Get message options structure)
  https://www.ibm.com/support/knowledgecenter/
  SSFKSJ_8.0.0/com.ibm.mq.ref.dev.doc/q091510_.htm
  .
  The issue occurs, when backing-out non-persistent
  work (in this case the MQGET from QMGR).
  CSQIRREQ is invoked to back-out the non-persistent
  work, and passes an uninitialised variable,
  dummyLRH, to CSQIUNDO.
  If the storage 4 bytes past the start of dummyLRH
  contains a residual value of x2000,
  the non-persistent MQGET etc is not backed-out
  (so the IRH is left as 'deleted', and the
  queue-depth is not incremented).
  .
  When using an indexed queue this results in
  the IKR remaining on the chain for the queue,
  although the message is deleted, resulting in
  the subsequent 5C6-00C90F00 abend.
  Note that the storage at 4 bytes past the start
  of dummyLRH was previously used for the last 4
  bytes of a log RBA, so the problem only occurs
  with a log RBA ending in 2000xxxx is currently
  in use.
  .
  Additional Symptom(s) Search Keyword(s):
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED:                                              *
  * All users of IBM MQ for z/OS Version 9 Release 0             *
  * Modification 0.                                              *
  ****************************************************************
  * PROBLEM DESCRIPTION:                                         *
  * Abend 5C6-00C90F00 for an indexed queue following the        *
  * backout of an MQGET.                                         *
  ****************************************************************
  * RECOMMENDATION:                                              *
  * None                                                         *
  ****************************************************************
  Backout processing runs for an MQGET of a non-persistent message
  on an indexed private queue. CSQIRREQ runs to back-out the
  non-persistent work, and calls CSQIUNDO, passing it a dummy log
  record header, dummyLRH. However dummyLRH is not initialised,
  and contains residual storage. If the storage 4 bytes past the
  start of dummyLRH contains a residual value of x2000, CSQIUNDO
  interprets this as log record type LRHRMC2, a coupling facility
  manager record for a shared queue for which no processing is
  required, so the MQGET is not backed-out. The IRH message record
  header is left marked as 'deleted', and the queue-depth is not
  incremented.
  Further backout processing resets the uncommitted get flag
  fucom_get in the IKR (Keyed Read Block), such that when CSQIMGEF
  runs for a subsequent MQGET it finds the IKR on the chain for
  the queue. It also finds that the message referenced by the IKR
  is deleted, and Abends with code 5C6-00C90F00,
  CSQI_RECORD_DELETED.
  Note that the storage at 4 bytes past the start of dummyLRH was
  previously used for the last 4 bytes of a log RBA, so the
  problem only occurs when a log RBA ending in 2000xxxx is
  currently in use.
  
  This problem may result in other symptoms, including:
  Abend 5C6-00C93100, CSQI_KEYED_READ_FAILURE.
  Messages could also be lost, or returned from the wrong queue.
  

Problem conclusion

• CSQIRREQ has been changed to initialise dummyLRH before passing
  it on the call to CSQIUNDO.
  000Y
  CSQIRREQ
  

Temporary fix

Comments

APAR Information

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

  PI77968

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

  UI46402

Modules/Macros

• CSQIRREQ none
  

Fix information

• Fixed component name

  MQ Z/OS V9

• Fixed component ID

  5655MQ900

Applicable component levels

• R000 PSY UI46402

     UP17/05/19 P F705 ¢

Fix is available

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