PI69443: MQ Z/OS - HIGH CPU CONSUMPTION IN CHIN

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• A negative recv() timeout value is being calculated as the
  interval between the current time and the time that some
  non-heartbeat data was last received is greater than the
  configured DISCINT value for client channel. This negative
  recv() timeout value results in the high CPU in the CHIN.
  

Local fix

• The problem could be circumvented by setting DISCINT to 0 for
  SVRCONN
  

Problem summary

• ****************************************************************
  * USERS AFFECTED:                                              *
  * All users of IBM MQ for z/OS Version 9 Release 0             *
  * Modification 0.                                              *
  ****************************************************************
  * PROBLEM DESCRIPTION:                                         *
  * High CPU usage reported in CHIN when using SHARECNV>0        *
  * SVRCONN channels with disconnect interval configured.        *
  ****************************************************************
  * RECOMMENDATION:                                              *
  * N/A                                                          *
  ****************************************************************
  Client applications executing MQGET with unlimited or very long
  wait intervals connected using SHARECNV >0 SVRCONN channels with
  disconnect interval (DISCINT) configured with a value smaller
  than the MQGET WAIT interval can cause the invocation of TCPIP
  receive calls with negative timeout values causing the receive
  to return immediately with a reason code indicating that timeout
  interval has expired resulting in a loop of receive calls
  expecting data or a heartbeat message or DISCINT to expire. This
  loop causes the high CPU usage observed.
  

Problem conclusion

• CSQXCCAX (cciReceiveOne) has been changed to prevent passing
  negative timeout intervals to the TCP IP receive calls avoiding
  the loop.
  

Temporary fix

Comments

APAR Information

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

  PI62878

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

  UI41144

Modules/Macros

• CSQXCCAX
  

Fix information

• Fixed component name

  MQ Z/OS V9

• Fixed component ID

  5655MQ900

Applicable component levels

• R000 PSY UI41144

     UP16/10/14 P F610 ¢

Fix is available

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