PH29314: ABEND 878-0C - SUBPOOL 229 KEY 7 FILLED WITH DXWB AND EKTM

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• APAR PH03837 (MQ V9.0 and V9.1) and PH02959 (MQ V8) improved
  the efficiency of storing multiple DXWB blocks and the capacity
  was increased by a factor of 30.
  
  This new APAR was submitted to check if it is possible to
  provide further improvements, this time by enhancing the code
  so that when XCF path saturation is detected we release some
  additional latches which should allow MQ to process any
  outstanding DXWB notifications more quickly. In addition, there
  is some code that under certain circumstances introduces an
  small, intentional pause which was intended to protect the
  admin structure from filling up in certain circumstances, but
  in recent years further enhancements to the way queue managers
  directly communicate with each other may have rendered this
  code obsolete and bypassing it may provide significant
  improvements in DXWB processing speed again. Furthermore, we
  believe there are also possible enhancements when the trigger
  message is being delivered to the local queue manager rather
  than going through XCF.
  
  These additional options will be investigated to determine
  which ones may provide additional relief.
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All users of IBM MQ for z/OS Version 9       *
  *                 Release 1 Modification 0 and Release 2       *
  *                 Modification 0.                              *
  ****************************************************************
  * PROBLEM DESCRIPTION: Abend S878 occurs when using            *
  *                      TRIGTYPE(EVERY) with shared application *
  *                      queues, due to a build up of DXWB/EKTM  *
  *                      control blocks.                         *
  ****************************************************************
  CSQ5XWK1 processing of incoming DXWBs for trigger every
  notifications was delayed due to latch contention. The incoming
  notifications all originated on the local queue manager.
  
  The volume of notifications being sent resulted in there being
  no available paths, causing the sending task to suspend before
  retrying. This led to latch contention between the sending tasks
  and CSQ5XWK1, causing a build up of DXWBs waiting to be
  processed.
  

Problem conclusion

• CSQEWCMQ is changed to deliver trigger every notifications for
  the local queue manager without using XCF, avoiding the latch
  contention between the sending and receiving tasks.
  

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:

  010PC2Ÿ UI73265 UI73266

Modules/Macros

• CSQEKATM CSQEWCMQ CSQMKATM CSQNCRSP CSQNRTS  CSQNSGRP CSQNSRSP
  

Fix information

• Fixed component name

  IBM MQ Z/OS V9

• Fixed component ID

  5655MQ900

Applicable component levels

• R100 PSY UI73266

     UP21/01/28 P F101 ¢

• R200 PSY UI73265

     UP21/01/28 P F101 ¢

Fix is available

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