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PM54748: FOLLOWING A DB2 CANCEL OF A DB2 THREAD BEING PROTECTED BY A CICS REGION, DFHAP0002 CODE 3255 . THEN LATER, CTHREAD MAX REACHED.

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APAR status

  • Closed as program error.

Error description

  • With a DB2 command, you cancelled some threads that were
    owned by a CICS region.  These threads were protected threads
    that were not being used by a CICS transaction.  At time of
    cancel, CICS issues the following message / dump:
    .
    DFHAP0002 CICSAPPL A severe error (code X'3255') has occurred in
    module DFHD2D2 .
    .
    Following that the CICS region is back to normal for a couple
    hours until tasks in this CICS region, as well as in other
    applications connected to DB2 start having SQL calls hang.  This
    is caused by DB2 reaching cthread max .  That causes SQL calls
    to hang while queued in QT* status in DB2 as there are no more
    available threads.   An unusually large number of threads are
    threads in TD status owned by the CICS region that issued the
    DFHAP0002 message.
    .
    In the DFHAP0002 dump, the 'DB2=3' formatter shows that the
    CSUB owned by the CEX2 task has as CSUB trace showing the
    following as its last 2 entries:
    .
    1F00024C C1E2E2D6 00000000 00000000  *...<ASSO
    2000024C 5CD9C5C3 0000004E 00E50013  *...<*REC
    .
    Those entries show a successful ASSOciate , followed by the
    abend04E reason 00E50013 indicative of the cancel.
    .
    Then in a dump taken later after tasks have hung up, if you
    find in the 'DB2=3' output on 00024C , you get lots of hits
    like this one:
    .
    6300024C C1E2E2D6 00000000 00F31101 *...<ASSO.....3..
    .
    This shows task 24 trying and failing to associate to a
    protected thread it wants to terminate.  The reason 00F31101
    means that the D2 TCB (on which CEX2 is running) is already
    associated to a different thread.  That thread would be the
    one it successfully ASSOciated to just prior to the abend04E
    reason 00E50013 caused by the cancel.  This prevents the CEX2
    from terminating any protected threads.  Eventually that causes
    DB2 to reach cthread max, at which point this CICS and other
    DB2 applications start having SQL calls hanging in DB2 .
    

Local fix

Problem summary

  • ****************************************************************
    * USERS AFFECTED: All                                          *
    ****************************************************************
    * PROBLEM DESCRIPTION: Message 'DFHAP0002 A severe error error *
    *                      (code X'3255') has occurred in module   *
    *                      DFHD2D2' is received following the DB2  *
    *                      cancel of a protected thread.           *
    ****************************************************************
    * RECOMMENDATION:                                              *
    ****************************************************************
    A DB2 protected thread is in the process of being terminated by
    CEX2. After successfully associating the D2 TCB to that thread,
    a DB2 Cancel occurs. The cancel leads to the D2 TCB
    suffering an abend04E, which subsequently causes the x'3255'
    error within DFHD2D2. As a consequence, the DB2 subsystem can
    reach its CTHREAD limit, causing the system to become
    unresponsive.
    Additional keywords: 04E S04E
    

Problem conclusion

  • DFHD2D2 has been amended such that, within its recovery routine,
    if it has been called during a terminate_thread, a call to
    issue_db2_dissociate is made.
    

Temporary fix

  • FIX AVAILABLE BY PTF ONLY
    

Comments

  • ž**** PE13/03/12 FIX IN ERROR. SEE APAR PM79809  FOR DESCRIPTION
    ž**** PE13/01/17 FIX IN ERROR. SEE APAR PM80818  FOR DESCRIPTION
    

APAR Information

  • APAR number

    PM54748

  • 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

    2011-12-20

  • Closed date

    2012-03-27

  • Last modified date

    2013-04-09

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

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

    PM57244 UK77435 UK77436

Modules/Macros

  •    DESD2D2  DFHD2D2
    

Fix information

  • Fixed component name

    CICS TS Z/OS V4

  • Fixed component ID

    5655S9700

Applicable component levels

  • R600 PSY UK77435

       UP12/04/03 P F204

  • R700 PSY UK77436

       UP12/04/03 P F204

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:
09 April 2013