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PM31494: 32K FIXED CSM DATASPACE BUFFER GROWTH CONTAINING IUDR PACKING BUFFERS

A fix is available

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APAR status

  • Closed as program error.

Error description

  • There is a spike in CSM fixed 32K dataspace buffers filled with
    IUDR packing buffers that contains packets already sent outbound
    and are waiting to be released or reused until the timer
    expires.  The packing buffers should be freed sooner.  This
    spike could cause CSM fixed storage to become constrained.
    .
    KEYWORDS: IUDR blocking factor group
    .
    VERIFICATION STEPS:
    There is not data on the tcp or ucb send queues.
    .
    The 32K CSM dataspace buffers are fixed and contain IUDRs with
    SPACs in them.  The SPACs are on the TSEB_QDIO_BGRP_Q@
    

Local fix

Problem summary

  • ****************************************************************
    * USERS AFFECTED: All users of the IBM Communications Server   *
    *                 for z/OS Version 1 Release(s) 10, 11, and    *
    *                 12 IP                                        *
    ****************************************************************
    * PROBLEM DESCRIPTION: TCP/IP is not responsive to CSM FIXED   *
    *                      constrained or critical state when      *
    *                      releasing Blocking Groups (BGRP) and    *
    *                      associated packing buffers.             *
    ****************************************************************
    * RECOMMENDATION:                                              *
    ****************************************************************
    TCP/IP is not responsive to CSM FIXED constrained or critical
    state when releasing Blocking Groups (BGRP) and associated
    packing buffers.
    BGRPs are used to improve the efficiency of passing outbound
    packets to the device layer (DLC).  BGRPs and their associated
    packing buffers are allocated in CSM Dataspace and must be page
    fixed for the DLC.  When a BGRP has been processed by the DLC
    it is placed on a cache queue.  The BGRP cache queue is scanned
    periodically and old BGRPs are released.
    The BGRP cache scan logic does not take into account the state
    of CSM.  This can lead to a CSM FIXED constrained or critical
    state persisting longer than necessary when large numbers of
    BGRPs are cached.
    +-------------------------------------------------------------+
    + Please check our Communications Server for OS/390 homepages +
    + for common networking tips and fixes.  The URL for these    +
    + homepages can be found in Informational APAR II11334.       +
    +-------------------------------------------------------------+
    

Problem conclusion

  • EZBIFOB1 has been amended to take the CSM FIXED state into
    account during BGRP cache scans.  BGRPs and associated packing
    buffers will be aggressively released when CSM is in a FIXED
    constrained or critical state.
    
    * Cross Reference between External and Internal Names
    

Temporary fix

Comments

APAR Information

  • APAR number

    PM31494

  • Reported component name

    TCP/IP V3 MVS

  • Reported component ID

    5655HAL00

  • Reported release

    1A0

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt / Xsystem

  • Submitted date

    2011-01-28

  • Closed date

    2011-03-04

  • Last modified date

    2011-04-04

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

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

    UK65650 UK65651 UK65652

Modules/Macros

  • EZBIFBP1
    

Fix information

  • Fixed component name

    TCP/IP V3 MVS

  • Fixed component ID

    5655HAL00

Applicable component levels

  • R1A0 PSY UK65650

       UP11/03/26 P F103

  • R1B0 PSY UK65651

       UP11/03/26 P F103

  • R1C0 PSY UK65652

       UP11/03/26 P F103

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 2011