PH59292: ABN=5C6-00E20045 REPORTED WHEN A 64-BIT STORAGE POOL FAILS TO EXPAND

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• Queue Manager was in hung status and a dump was taken for a
  abend 5C6-00E20045 when failing to expand a 64-bit storage pool
  (QP64) for LNAN control blocks. The expansion failed because
  MEMLIMIT had been reached. Leading up to the abend
  5C6-00E20045, message CSQY225E was issued for the QMGR going
  short-of-storage (SOS) for above the bar storage. This message
  is issued following a 64-bit storage contraction which fails to
  relieve the SOS situation. Flag LPVTSH64 is also set in the
  QMGR LPVT to indicate that this happened. While this flag is
  on, above the bar storage contraction won't be attempted again.
  This flag is usually turned off again when message CSQY226I is
  issued. The problem is that this flag isn't reset properly. The
  runaway application later ended and the LNAN which it allocated
  would have been freed back to the storage pool when its commit
  duration locks were released. LPVTSH64 still being on means any
  future failing above the bar storage requests won't attempt
  storage contraction, even though it would likely now be
  successful.
  

Local fix

•  - Increasing MEMLIMIT as already suggested should be the first
  step.
   - Tuning MAXUMSGS to a lower value than the default value of
  10,000 will also help prevent build-ups of large unit of work.
   - /cpf RECOVER QMGR(COMPRESS ALL64) will force 64-bit storage
  contraction to take place.
  

Problem summary

• ****************************************************************
  * USERS AFFECTED: All users ofIBM MQ for z/OS Version 9        *
  *                 Release 2 Modification 0,                    *
  *                 Release 3 Modification 0 and                 *
  *                 Release 4 Modification 0.                    *
  ****************************************************************
  * PROBLEM DESCRIPTION: Storage shortage above the bar as       *
  *                      reported by message CSQY225E is not     *
  *                      relieved.                               *
  *                      Eventually the Short on Storage (SOS)   *
  *                      condition can result in other symptoms  *
  *                      including, but not limited to:          *
  *                      - abend 5C6-00E20045                    *
  *                      - queue manager hang                    *
  ****************************************************************
  When storage above the bar is allocated, it is often allocated
  to internal pools which retain the storage when it is no longer
  required for performance reasons.
  When the available storage is less than 10% of the total
  available, CSQY224I is issued to report that the queue manager
  is short on storage, and storage contraction is initiated to
  release storage that has been retained.
  When this is unable to free sufficient storage message CSQY225E
  is issued to report the critical storage shortage.
  
  After CSQY225E is issued, no further storage contractions are
  scheduled, even as used storage is released back to the pools.
  

Problem conclusion

• Storage pool management routines have been changed to call
  storage contraction while the queue manager remains in a
  critical SOS condition, ensuring the condition is relieved as
  soon as storage can be safely released.
  

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:

  UI98415 UI98416 UI98417

Modules/Macros

• CSQSCTL  CSQSQC64
  

Fix information

• Fixed component name

  IBM MQ Z/OS V9

• Fixed component ID

  5655MQ900

Applicable component levels

• R200 PSY UI98417

     UP24/09/25 P F409 ¢

• R300 PSY UI98416

     UP24/09/25 P F409 ¢

• R400 PSY UI98415

     UP24/09/25 P F409 ¢

Fix is available

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