PH03468: MQ V9: S0C4 DISPATCHER PROCESS ERROR AFTER SEVERAL STOP CHANNEL COMMANDS

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• Abend 0C4 did happen in chinit after running
  a script to stop channels via command to terminate client
  connections. Some of the commands were issued twice against the
  same IP address.
  .
  Additional keywords:
  ABEND0C4 ABENDS0C4 S00C4
  

Local fix

• n.a.
  

Problem summary

• ****************************************************************
  * USERS AFFECTED: All users of IBM MQ for z/OS Version 9       *
  *                 Release 0 Modification 0 and Release 1       *
  *                 Modification 0.                              *
  ****************************************************************
  * PROBLEM DESCRIPTION: Issuing multiple 'STOP CHL(x)           *
  *                      CONNAME(x.x.x.x) MODE(FORCE)' commands  *
  *                      to the same channel produces an 0C4     *
  *                      ABEND.                                  *
  ****************************************************************
  Issuing multiple 'STOP CHANNEL(x) CONNAME(x.x.x.x) MODE(FORCE)'
  commands to the same channel produces an 0C4 ABEND.
  
  The ABEND is caused due to an attempt to CANCEL the channel
  multiple times via asynchronous calls from the multiple 'STOP
  CHANNEL' commands.
  
  This opens up a timing window where the second time an attempt
  is made to CANCEL the channel some storage has already been
  freed by the first attempt and hence the 0C4 is produced.
  

Problem conclusion

• Defensive code has been introduced to ensure that in the event
  that a call to CANCEL the same channel multiple times is made
  an 0C4 will not be produced. Additionally subsequent CANCEL
  channel calls to the same channel will not process the CANCEL.
  

Temporary fix

Comments

APAR Information

• APAR is sysrouted FROM one or more of the following:

  PI99255

• APAR is sysrouted TO one or more of the following:

  UI59902 UI59903

Modules/Macros

• CSQXSCAN
  

Fix information

• Fixed component name

  IBM MQ Z/OS V9

• Fixed component ID

  5655MQ900

Applicable component levels

• R000 PSY UI59902

     UP18/12/14 P F812

• R100 PSY UI59903

     UP18/12/15 P F812

Fix is available

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