PH59468: HIGH MSTR CPU DUE TO A BUILD UP OF LOCKS FROM CSQIDBLK

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• The client noticed a very high CPU usage of queue manager
  started task procedures on z/OS. The dump shows higher SRB time
  by MSTR address space and a huge number of allocation locks.
  The problem occurs when browsing a shared queue using MQGET
  option MQGMO_LOGICAL_ORDER. The problem results in a build up
  of locks from CSQIDBLK. These locks are not released until
  agent deallocation. For a bindings application this will be
  when the last thread from an application disconnects from the
  QMGR. For client connections, CHIN adapter agent deallocation
  does not occur until the CHIN is stopped.
  

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: High CPU is observed in the Queue       *
  *                      Manager address space when browsing a   *
  *                      shared queue with the MQGET option      *
  *                      MQGMO_LOGICAL_ORDER.                    *
  ****************************************************************
  When browsing a shared queue with the MQGET option
  MQGMO_LOGICAL_ORDER, CPU usage is notably increased due to
  unnecessary attempts to obtain browse cursor locks. These locks
  are not deallocated until either:
  
  - The last thread from an application disconnects from the Queue
    Manager when using bindings connections.
  - The Channel Initiator is stopped when using client
    connections.
  

Problem conclusion

• The code has been changed so that the unnecessary browse cursor
  locks are no longer obtained when browsing a shared queue with
  the MQGET option MQGMO_LOGICAL_ORDER.
  

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:

  UI97272 UI97967

Modules/Macros

• CSQIDBLK
  

Fix information

• Fixed component name

  IBM MQ Z/OS V9

• Fixed component ID

  5655MQ900

Applicable component levels

• R300 PSY UI97272

     UP24/06/27 P F406

• R400 PSY UI97967

     UP24/09/25 P F409

Fix is available

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