PH38302: CICS HANG, DEADLY EMBRACE, DSITLOCK AND XMLOCK

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• A potential deadly embrace can result with CICS transaction CQRC
  holding the DSITLOCK and then queueing for the XMLOCK. Other
  tasks may already have the XMLOCK and need the DSITLOCK. When
  this occurs, a deadly embrace is created and CICS will be hung.
  
  For the case that this APAR was created, the other transaction
  was CLR2, which owned the XMLOCK but also was waiting for the
  DSITLOCK.
  
  
  Additional Symptoms and Keywords: KIXREVGJT
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All CICS users.                              *
  ****************************************************************
  * PROBLEM DESCRIPTION: Deadlock between two CICS tasks, one    *
  *                      trying to attach the CQRC transaction   *
  *                      and the other a CLQR transaction.       *
  ****************************************************************
  CICS initialisation drives DFHDSDM to attach a CQRC
  transaction. The DSITLOCK is still held when the attach is
  driven. Meanwhile, another KE stack is trying to attach a
  CLQR transaction. As txdstat_int_attaches happens to have
  reached txdstat_next_decay (d20), DFHXMAT has to call
  DFHDSITM to inquire on OTE information from the dispatcher.
  It does this while holding the XMLOCK. Since both stacks hold
  the respective lock that the other now needs they are
  deadlocked. CICS had to be cancelled and restarted to resolve
  the hang.
  

Problem conclusion

• DFHDSDM has been changed to release the DSITLOCK once state in
  the dispatcher has been updated, and before the attempt to
  attach CQRC.
  

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:

  UI76585

Modules/Macros

• DFHDSDM
  

Fix information

• Fixed component name

  CICS TS Z/OS V5

• Fixed component ID

  5655Y0400

Applicable component levels

• R300 PSY UI76585

     UP21/08/13 P F108 ¢

Fix is available

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