PH66280: ABN=60D-00000000,U= ,C=MQ900.930.SSSC-CSQ3CL0X,M=CSQ3CL0X AND ABN=5C6-00E50001,U=XXXXXXXX,C=MQ900.930.ASMC-CSQVCRTH,M=CSQVCFRR,

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• The root cause of both the S60D and subsequent 5C6-00E50001 is
  freed ACE being present on the ending application's VLCAAACE
  chain. The freed ACE caused an 0C4 in CSQ3SSI2, which was
  recovered by CSQ3SSES however this also abended 0C4 for the same
  reason - CSQ3SSES was repeatedly called, abending 0C4 each time,
  until the task was abended S60D. This is the same underlying
  situation which led to the creation of diagnostic APAR PH65668
  to detect the error earlier, due to a significant elapsed time
  between an earlier abend involving the problematic ACE and the
  subsequent symptoms. In this instance the dumps were closer to
  the earlier abends, and a scenario was identified that can lead
  to the ACE being freed without being correctly removed from the
  VLCAAACE chain during recovery processing, leading to the
  reported problems occurring later when the VLCAAACE chain is
  used. This has also confirmed that the problem requires specific
  timing conditions in recovery processing to occur, and is
  unrelated to recent maintenance. There are a couple of things
  that need to be addressed here: 1) CSQ3SSES shouldn't repeatedly
  abend 0C4 if a freed ACE is found on the chain. 2) The ACE
  should not be freed while still on an ally's VLCAAACE chain
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All users of IBM MQ for z/OS Version 9       *
  *                 Release 3 Modification 0 and Release 4       *
  *                 Modification 0.                              *
  ****************************************************************
  * PROBLEM DESCRIPTION: Unpredictable behaviour occurs          *
  *                      following abnormal termination of an    *
  *                      RRS task, if the context ACE is         *
  *                      subsequently used from another address  *
  *                      space.                                  *
  *                      Symptoms can include:                   *
  *                      - Abend S60D due to a recovery loop for *
  *                      abend S0C4 in CSQ3SSES                  *
  *                      - Abend S5C6-00E50032 in CSQVDISC       *
  *                      - Abnormal queue manager termination    *
  *                      S6C6                                    *
  ****************************************************************
  Following abnormal termination of an RRS task that was executing
  in the queue manager, if the context is disassociated from the
  task without ending, the context ACE can remain on the VLCA
  chain for the application. When the context is used from another
  address space (for example, for further MQ work, or when the
  context is ended), the ACE is added to a second VLCA chain. When
  the ACE is subsequently freed, this leads to corruption of the
  VLCA chains, leading to various symptoms.
  

Problem conclusion

• When CSQ3SSES detects that a freed ACE has been added to a VLCA
  chain, it will terminate the queue manager S6C6 to protect the
  queue manager integrity.
  CSQMCPRH and CSQ3RRSM are changed to correctly detect if the
  context ACE is already on a different VLCA chain and remove it,
  before adding it to the current address space's VLCA chain.
  

Temporary fix

Comments

APAR Information

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

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

  UO06694 UO06695

Modules/Macros

• CSQ3RRSM CSQ3SSES CSQMCPRH
  

Fix information

• Fixed component name

  IBM MQ Z/OS V9

• Fixed component ID

  5655MQ900

Applicable component levels

• R300 PSY UO06695

     UP26/02/14 I 1000

• R400 PSY UO06694

     UP26/02/14 I 1000

Fix is available

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