PH47682: ABEND 0C4-4 LOC=CSQXRCTL.CSQXRMRS OCCURED WHEN TYPE(BLOCKADDR) WARN(NO) CHLAUTH RULE

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• The 0C4 abend below occurred while suspending a connection
  blocked by a TYPE(BLOCKADDR) CHLAUTH rule. The listener process
  was in the process of adding the conversation to a hold chain
  to be processed by a separate process which runs on a
  dispatcher. It had got as far as loading the head pointer to
  the chain, at which point the listener TCB was un-dispatched
  due to an external timer interrupt.
  ABN=
  0C4-00000004,M=CSQXESTX,LOC=CSQXRCTL.CSQXRMRS
  
  The conversation at the head of the chain was freed by the
  scheduled dispatcher process, and the storage reused, in the
  time before the listener TCB was re-dispatched. When the
  listener TCB was re-dispatched and continued to run the chain,
  it chained into key 0 storage. The listener subsequently
  abended 0C4-04 when trying to set the chain pointer in this key
  0 storage.
  
  The problem is inadequate serialization between the listener
  task and a dispatcher process when blocking a connection with a
  TYPE(BLOCKADDR) WARN(NO) CHLAUTH rule.
  Keyword CSQXRMRS
  

Local fix

• N/A
  

Problem summary

• ****************************************************************
  * USERS AFFECTED: All users of IBM MQ for z/OS Version 9       *
  *                 Release 1 Modification 0,                    *
  *                 Release 2 Modification 0, and                *
  *                 Release 3 Modification 0.                    *
  ****************************************************************
  * PROBLEM DESCRIPTION: Abend S0C4 occurs in CSQXRCTL.CSQXRMRS  *
  *                      when multiple incoming connections are  *
  *                      blocked by CHLAUTH BLOCKADDR rules.     *
  ****************************************************************
  When an incoming connection is blocked due to a CHLAUTH
  BLOCKADDR rule, the conversation is held for a period of time
  prior to being closed.
  A timing window exists where a conversation is being added to
  the chain of such 'held' conversations at the same time as an
  earlier held conversation in the chain is removed and freed.
  This can result in an access to freed/reused storage, resulting
  in the reported 0C4 abend.
  

Problem conclusion

• The serialisation used when adding or removing held
  conversations from the chain has been corrected.
  

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:

  UI82769 UI82770 UI82771

Modules/Macros

• CSQXRMRS
  

Fix information

• Fixed component name

  IBM MQ Z/OS V9

• Fixed component ID

  5655MQ900

Applicable component levels

• R100 PSY UI82771

     UP22/10/22 P F210

• R200 PSY UI82770

     UP22/10/22 P F210

• R300 PSY UI82769

     UP22/10/22 P F210

Fix is available

• Select the PTF appropriate for your component level. You will be required to sign in. Distribution on physical media is not available in all countries.