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PI62878: MQ 8.0 Z/OS - HIGH CPU CONSUMPTION IN CHIN

A fix is available

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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 WebSphere MQ for z/OS Version 8 *
    *                 Release 0 Modification 0.                    *
    ****************************************************************
    * PROBLEM DESCRIPTION: High CPU usage reported in CHIN when    *
    *                      using SHARECNV>0  SVRCONN channels with *
    *                      disconnect interval configured.         *
    ****************************************************************
    * RECOMMENDATION:                                              *
    ****************************************************************
    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.
    000Y
    CSQXCCAX
    

Temporary fix

  • *********
    * HIPER *
    *********
    

Comments

APAR Information

  • APAR number

    PI62878

  • Reported component name

    WMQ Z/OS 8

  • Reported component ID

    5655W9700

  • Reported release

    000

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    YesHIPER

  • Special Attention

    NoSpecatt / Xsystem

  • Submitted date

    2016-05-24

  • Closed date

    2016-09-21

  • Last modified date

    2016-11-02

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

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

    PI69443 PI69444 UI40926

Modules/Macros

  • CSQXCCAX
    

Fix information

  • Fixed component name

    WMQ Z/OS 8

  • Fixed component ID

    5655W9700

Applicable component levels

  • R000 PSY UI40926

       UP16/10/06 P F610 ¢

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.

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Document Information

Modified date:
02 November 2016