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PM84828: DFHDD0002 SEVERE ERROR (CODE X'0406') IN DFHDDBR DFHDD0001 ABEND (CODE ---/AKEC) AT X'FFFF' IN DFHDDBR

A fix is available

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APAR status

  • Closed as program error.

Error description

  • You are receiving the following messages:
    DFHDD0002  A severe error (code X'0406') has
               occurred in module DFHDDBR.
     DFHDD0001  An abend (code ---/AKEC) has occurred
               at offset X'FFFF' in module DFHDDBR.
    .
    In the trace, you see the following trace entries prior to
    an Invalid_browse exception trace entry:
    98350 QR    DD 0401 DDBR  ENTRY
        GET_NEXT_ENTRY ENTRY_NAME(2A651490,80000000,00000028)
        DIRECTORY_TOKEN(28A0B610)
        BROWSE_TOKEN(2AB283C0)
        DIRECTORY_NAME(USD1)
    DM    CO    DD 0401 DDBR  ENTRY
        GET_NEXT_ENTRY ENTRY_NAME(2E9658B0,00000028,00000028)
        DIRECTORY_TOKEN(28A0B610)
        BROWSE_TOKEN(2AB28290)
        DIRECTORY_NAME(USD1)
    98350 QR    DD 0406 DDBR  *EXC*
        Invalid_browse FUNCTION(GET_NEXT_ENTRY)
        ENTRY_NAME(2A651490,80000000,00000028)
        DIRECTORY_TOKEN(28A0B610)
        BROWSE_TOKEN(2AB283C0)
        DIRECTORY_NAME(USD1)
    .
    On further diagnosis, DD0002 occurs when 2 tasks running on
    2 different TCBs both initiate browses on the same directory
    - USD1 directory. The first browse occurs as part of a
    DFHUSAD VALIDATE_USERID, which is driven as part of an
    EXEC CICS START TRANSID USERID. This runs on the QR TCB.
    The second is a NOTIFY_USERID call, which runs on the CO TCB.
    This is driven when an ENF notify occurs because something
    has changed in the external security manager, such as a
    USERID being revoked or being CONNECTED or REMOVED from
    a RACF group. DFHDDBR START_BROWSE getmains a browse element
    and adds it to the head of the browse element chain for the
    USD1 directory (field dh_current_browses). This is a push
    down stack of browse elements. When DFHDDBR GET_NEXT is
    called, the caller passes the browse element on the call,
    and GET_NEXT processing runs down the dh_current_browses
    chain to confirm that a valid browse token has been found.
    The failure to locate the token results in a DD 0406
    exception trace and DD0002 system dump.
    .
    The DD0001/abendAKEC with the loop occurs because the
    dh_current_browses chain points to a browse element whose
    bv_next pointer points to itself.
    .
    Additional Symptom(s) Search Keyword(s):
    DFHUSAD DFHDDBRWS
    KIXREVSLD
    

Local fix

Problem summary

  • ****************************************************************
    * USERS AFFECTED: All CICS users                               *
    ****************************************************************
    * PROBLEM DESCRIPTION: MSGDFHDD0002 severe error code 0406 in  *
    *                      DFHDDBR when 2 tasks browse the USD1    *
    *                      directory in parallel.                  *
    ****************************************************************
    * RECOMMENDATION:                                              *
    ****************************************************************
    EXEC CICS START TRANSID USERID is issued by a task. This calls
    DFHUSAD VALIDATE_USERID which triggers a browse of the USD1
    directory to locate the USERID. This runs on the QR TCB.
    In parallel, an ENF notify causes DFHUSAD NOTIFY_USERID to run
    because a USERID's state has been updated. The NOTIFY_USERID
    call runs under a long-running task which executes on the CO
    TCB. It only runs on the CO TCB if SUBTSKS=1 is in the SIT.
    DFHDDBR START_BROWSE is issued by both tasks in parallel. Both
    calls create browse elements. These are appended to the
    dh_current_browses chain for the USD1 directory.
    
    The code which updates this chain isn't single threaded. The
    second task to update the chain overwrites the reference to
    the browse element created by the first task.
    When the first task calls DFHDDBR for function GET_NEXT, DFHDDBR
    cannot locate the browse element and raises a severe error
    which results in DFHDD0002 with severe error code 0406.
    The corruption of the browse element chain can lead to other
    errors such as DFHDD0001 for loops in DFHDDBR.
    
    ADDITIONAL KEYWORDS :- MSGDFHDD0001 DD0001 AKEC
    

Problem conclusion

  • DFHDDBR START_BROWSE and END_BROWSE functions have been changed
    to obtain exclusive locks on the directory while the browse
    element chain is being updated.
    

Temporary fix

  • FIX AVAILABLE BY PTF ONLY
    

Comments

APAR Information

  • APAR number

    PM84828

  • Reported component name

    CICS TS Z/OS V4

  • Reported component ID

    5655S9700

  • Reported release

    600

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt

  • Submitted date

    2013-03-14

  • Closed date

    2013-06-03

  • Last modified date

    2013-07-02

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

    PM62692

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

    UK94855

Modules/Macros

  •    DFHDDBR  DFHDDBRT
    

Fix information

  • Fixed component name

    CICS TS Z/OS V4

  • Fixed component ID

    5655S9700

Applicable component levels

  • R600 PSY UK94855

       UP13/06/10 P F306

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 July 2013