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PI74908: HIGH CPU UTILIZATION IN THE TCP/IP ADDRESS SPACE ACTING AS SYSPLEX DISTRIBUTOR

A fix is available

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APAR status

  • Closed as unreproducible in next release.

Error description

  • The CPU utilization in the TCP/IP address space is higher in
    V2R2 than prior releases when sysplex distributing a high volume
    of short lived connections.  The sysplex distribution of a new
    connection is generating a storage obtain and when the
    connection terminates there is an associated storage release.
    Prior to V2R2 the storage object was obtained from a cache
    queue, thus avoiding the storage obtain and release.  The
    majority of the CPU increase is attributed to contention on the
    local lock when multiple SRBs are processing concurrently.
    

Local fix

Problem summary

  • ****************************************************************
    * USERS AFFECTED:                                              *
    * All users of the IBM Communications Server for z/OS Version  *
    * 2 Release 2 IP:  Sysplex Distributor and Dynamic VIPA        *
    ****************************************************************
    * PROBLEM DESCRIPTION:                                         *
    * Performance slowdown for short lived connections to a DRVIPA *
    * at the Sysplex Distributor.  The slowdown may also be        *
    * present at the target system, or the owning system for a     *
    * Dynamic VIPA.                                                *
    ****************************************************************
    * RECOMMENDATION:                                              *
    * Apply PTF                                                    *
    ****************************************************************
    Changes introduced in V2R2 caused the Connection Route Hash
    Table Entry (CRHTE) used to represent a distributed connection
    to grow in size.  The new size did not fit into the storage
    caching model for TCPIP so all CRHTE control blocks resulted in
    a storage obtain when the connection initiated and a storage
    release when the connection terminated.  The CRHTE is obtained
    from TCPIP LSQA which requires the local lock to be held across
    the storage request.  Under heavy loads this additional storage
    obtain and release may cause contention on the local lock.  The
    contention on the local lock causes units of work to be
    suspended and resumed which requires additional CPU and
    introduces delays in the workflow.
    Targets for Distributed Dynamic VIPAs and owners of Dynamic
    VIPAs also create a CRHTE to track the state of all Dynamic VIPA
    related connections in the event the Distrubutor function is
    moved, or the Dynamic VIPA ownership is moved.  The storage
    obtains and releases for these endpoints may also see an
    increase in CPU utilization.
    

Problem conclusion

  • The storage caching model in TCPIP has been amended to account
    for the new CRHTE size.
    

Temporary fix

Comments

APAR Information

  • APAR number

    PI74908

  • Reported component name

    TCP/IP V3 MVS

  • Reported component ID

    5655HAL00

  • Reported release

    220

  • Status

    CLOSED UR1

  • PE

    NoPE

  • HIPER

    YesHIPER

  • Special Attention

    NoSpecatt / Xsystem

  • Submitted date

    2017-01-13

  • Closed date

    2017-02-23

  • Last modified date

    2017-04-04

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

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

    UI44952

Modules/Macros

  • EZBITSTO
    

Fix information

  • Fixed component name

    TCP/IP V3 MVS

  • Fixed component ID

    5655HAL00

Applicable component levels

  • R220 PSY UI44952

       UP17/03/31 P F703 ¢

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:
04 April 2017