PM77094: FOR COUPLING FACILITY USERS THAT OFFLOAD MESSAGES TO SMDS QMGR RECOVERY IS IMPACTED BY INSUFFICIENT STORAGE IN CF

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• When a queue manager recovers the CF structure (following a
  cancel of the QMGR and deletion of the structure) it does so by
  reading through the logs of all QMGRs in the QSG and replaying
  them. Then the latest backup from the QMGR log which took it
  is restored. While log replay completes quickly the QMGR
  recovery of the backup takes much longer. Recovery failure in
  this scenario is due to insufficient storage in the CF.
  To avoid this recovery failure of the CF structure the QMGR
  should connect to the CF structure with a 2:1 element to entry
  ratio at the time of structure initialization. This will be
  allowed if at least one of the offloading rules has a threshold
  and size of zero.
  ADDITIONAL SYMPTOM
  2192 MQRC_STORAGE_MEDIUM_FULL
  CSQE022E CSQERCF2 Structure x unusable, size is too small
  ABEND5C6 00C51173 CSQERCF2+000020F0
  CSQE035E CSQEQSR1 Structure x in failed state,recovery needed
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All users of WebSphere MQ for z/OS Version 7 *
  *                 Release 1 Modifcation 0.                     *
  ****************************************************************
  * PROBLEM DESCRIPTION: When using SMDS offload with at least   *
  *                      one of the offload rules having the     *
  *                      size and threshold set to zero, all of  *
  *                      the messages will be offloaded and for  *
  *                      each entry used in the CF structure,    *
  *                      only 2 elements will be used. When      *
  *                      ALLOWAUTOALT is not set on the CFRM     *
  *                      policy, about 60% of space in the       *
  *                      structure remains unused.               *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  The entry to element ratio for a structure is set on the first
  IXLCONN call. MQ has a fixed 1:6 ratio.
  However, if all the messages are offloaded to SMDS, each message
  will use 1 entry and 2 elements to be stored, leaving 4 elements
  unused per message.
  If ALLOWAUTOALT is set, the system will determine if the ratio
  can be optimised when the FULLTHRESHOLD value is reached and
  reorganise the structure if possible. This would change the
  entry to element ratio to 1:2 in the mentioned use case.
  This operation takes time however, and could cause applications
  to receive 2192 return codes.
  

Problem conclusion

• A service parm was added in this fix to initialise the CF
  Structure with a 1:2 entry to element ratio if all of the
  following conditions are true:
   - The service parm is set
   - SMDS offload is used, "OFFLOAD(SMDS)"
   - At least one of the offloading rules has the threshold and
     size values set to zero, for example
     "OFFLD1TH(0) OFFLD1SZ(0K)".
  
  The service parm should only be used under guidance of IBM
  support.
  
  MQSMDS/K
  100Y
  CSQECONN
  

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:

  UK90218

Modules/Macros

• CSQECONN
  

Fix information

• Fixed component name

  WMQ Z/OS V7

• Fixed component ID

  5655R3600

Applicable component levels

• R100 PSY UK90218

     UP13/01/16 P F301

Fix is available

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