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PM02532: ABEND04E RC00E20028 OCCURS REPEATEDLY AFTER A STORAGE OVERLAY

A fix is available

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APAR status

  • Closed as program error.

Error description

  • ABEND04E RC00E20028 occurred after a 1 byte storage overlay
    of an SKB control block.  The two bytes should be X'00AD'.
    However, they were X'01AD' for the incident reported.
    After the thread abended, its invalid SKB was neither
    validated nor cleaned up, and was put back on the free
    SKB chain for subsequent agents to pick up, which caused
    the abend to occur multiple times.
    
    Keywords: SMCOVERLAY
    DB2STGLK/K
    

Local fix

Problem summary

  • ****************************************************************
    * USERS AFFECTED: All DB2 V8 ( HDB8810 ) and V9 ( HDB9910 )    *
    *                 users.                                       *
    ****************************************************************
    * PROBLEM DESCRIPTION: ABEND04E RC00E20028 may occur           *
    *                      repeatedly on different threads for     *
    *                      the same SKB segment storage.  If the   *
    *                      abend occurs for a DB2 must-complete    *
    *                      thread, a subsystem termination occurs. *
    ****************************************************************
    * RECOMMENDATION:                                              *
    ****************************************************************
    Abends which occur due to STACK storage ( SKB ) validation
    overlays, result in ABEND04E RC00E20028.  The thread cleanup
    code then puts this damaged SKB back onto the stack cache
    without repairing the damage.  When this stack storage is
    allocated by another thread, the same abend will occur and
    if the overlaid SKB is being used by a DB2 must-complete
    process, DB2 terminates.
    

Problem conclusion

  • The modules which manage SKB stack storage have been changed to
    perform more validation as they are manipulating thread stack.
    If an overlay is detected, the thread will ABEND04E RC00E20028
    and during the abort cleanup process the overlaid SKB segment
    will be freemained rather than cached.  This will prevent
    multiple dumps occurring due to the same overlay and capture
    documentation closer to the actual overlay.
    

Temporary fix

Comments

APAR Information

  • APAR number

    PM02532

  • Reported component name

    DB2 OS/390 & Z/

  • Reported component ID

    5740XYR00

  • Reported release

    810

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt

  • Submitted date

    2009-12-01

  • Closed date

    2010-02-04

  • Last modified date

    2011-02-15

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

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

    UK54133 UK54134

Modules/Macros

  • DSNSPURS DSNSTACK DSNSVSTK
    

Fix information

  • Fixed component name

    DB2 OS/390 & Z/

  • Fixed component ID

    5740XYR00

Applicable component levels

  • R810 PSY UK54133

       UP10/02/23 P F002

  • R910 PSY UK54134

       UP10/02/23 P F002

Fix is available

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Document Information

Modified date:
15 February 2011