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PI94982: THREADING MODEL FOR LIBERTY CICS IS NEEDING THE XMATTLCK EXCLUSIVE CAUSING NEW TASKS TO NOT ATTACH. 18/04/24 PTF PECHANGE

A fix is available

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APAR status

  • Closed as program error.

Error description

  • You have several tasks in LMQUEUE suspends waiting on the
    XMATTLCK lock.   Normal attaches hold the XMATTLCK shared and
    new threading model for Liberty is designed to request the
    XMATTLCK exclusive.  This is causing a deadlock with the task
    needing the exclusive not getting it until all the shared tasks
    finish.
    

Local fix

Problem summary

  • ****************************************************************
    * USERS AFFECTED: All CICS users.                              *
    ****************************************************************
    * PROBLEM DESCRIPTION: Deadlock for XMATTLCK leads to          *
    *                      no transactions being attached          *
    *                      for two minutes.                        *
    ****************************************************************
    A CICS system is configured to accept work over MRO, and
    also through a Liberty JVM server running in the region.
    A routed transaction arrives and starts processing the
    attach for a new task. This task becomes a holder of the
    shared XMATTLCK.
    The transaction was routed over MRO, so begins to run the
    DFHMRXM primary client initialisation (INIT_XM_CLIENT) routine.
    Meanwhile, a web request arrives in a Liberty JVM server.
    A new task must be built for this request
    (using BUILD_TRANSACTION) and this new task requests the
    XMATTLCK as an exclusive lock.
    The original MRO task, still holding the XMATTLCK as a shared
    lock, then needs to attach a CITS task. This new CITS also
    needs to become an owner of the shared XMATTLCK, but cannot
    now do so due to the outstanding exclusive request for this
    same lock.
    This system is now deadlocked, and no transaction can be
    attached until a timeout occurs on the MRO task. This takes
    approximately two minutes.
    The original routing transaction will abend AZI6.
    .
    Additional Keywords: abendAZI6 abendAZTB abendAZVA AZTB AZVA
                         msgDFHAC2236 DFHAC2236
    

Problem conclusion

  • UI37614 UI39577 UI43335
    The CICS transaction attach mechanism has been updated
    to avoid the potential for this deadlock while initialising
    the primary client.
    

Temporary fix

Comments

APAR Information

  • APAR number

    PI94982

  • Reported component name

    CICS TS Z/OS V5

  • Reported component ID

    5655Y0400

  • Reported release

    000

  • Status

    CLOSED PER

  • PE

    YesPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt / Xsystem

  • Submitted date

    2018-03-12

  • Closed date

    2018-04-27

  • Last modified date

    2018-05-01

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

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

    PI95725 UI55545

Modules/Macros

  • DFHAPDUF DFHAPSDF DFHAPSI  DFHAPXM  DFHBRDUF DFHCQSY  DFHDBDUF
    DFHDPDUF DFHEJDUF DFHERM   DFHKETA  DFHMNDUF DFHMNXM  DFHMPDUF
    DFHPGDUF DFHREST  DFHSODUF DFHTKDUF DFHTMDUF DFHUEDUF DFHUSDUF
    DFHW2DUF DFHWBDUF DFHXMAB  DFHXMAT  DFHXMBD  DFHXMCL  DFHXMDD
    DFHXMDM  DFHXMDU2 DFHXMDUF DFHXMER  DFHXMFD  DFHXMIQ  DFHXMLD
    DFHXMQC  DFHXMQD  DFHXMRL  DFHXMRM  DFHXMRM1 DFHXMRP  DFHXMRSD
    DFHXMRU  DFHXMSR  DFHXMST  DFHXMTA  DFHXMXD  DFHXMXE  DFHXMXM
    

Fix information

  • Fixed component name

    CICS TS Z/OS V5

  • Fixed component ID

    5655Y0400

Applicable component levels

  • R000 PSY UI55545

       UP18/04/28 P F804 {

Fix is available

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Document Information

Modified date:
01 May 2018