PI96253: DFHLM0004 A POSSIBLE LOOP DETECTED IN MODULE DFHLMLM 18/05/08 PTF PECHANGE

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• After applying maintenance the customer is encountering a loop
  in module DFHLMLM (base level). This is occurring because the
  code in DFHLMLM UNLOCK_SHARED is in a loop trying to unlock
  XMATTLCK because its LM_CS_COUNT has gone negatve.
  .
  Additional Keywords:
  DFHLMLM DFHLM0004 LOOP XMATTLCK LM_CS_COUNT
  KIXREVACC
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All CICS Users with PI85926 applied.         *
  ****************************************************************
  * PROBLEM DESCRIPTION: CWXN can go into a tight loop which     *
  *                      results in message DFHLM0004 being      *
  *                      issued.                                 *
  ****************************************************************
  CICS has been up and running for a while and then issues
  message DFHLM0004 A possible loop has been detected at offset
  X'FFFF' in module DFHLMLM.
  The shared lock, XMATTLCK will be acquired. A code path
  in DFHXMAT will issue a change mode to the QR TCB, but if this
  is not required, because the task is already on the QR TCB,
  the function call type will be lost. This function call type
  is required to free the shared XMATTLCK.
  When enough transactions have executed which have acquired the
  lock but then not freed it, its lock count will go negative.
  When the next CWXN then tries to unlock the XMATTLCK code in
  DFHLMLM will loop because of the negative lock count.
  

Problem conclusion

• UI50631 UI51182 UI51932 UI53069
  DFHXMTA has been changed to ensure the function call type is not
  lost when the change mode is not required..
  

Temporary fix

Comments

APAR Information

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

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

  UI55321 UI55320

Modules/Macros

• DFH$CAT1 DFHD2DUF DFHD2EX1 DFHD2IN1 DFHD2IN2 DFHD2RP  DFHD2STP
  DFHD2STR DFHD2TM  DFHD2TRI DFHDSTCB DFHECIS  DFHECIST DFHECRL
  DFHECSC  DFHEIFC  DFHEIG   DFHEIP   DFHEPC   DFHERM   DFHFCDL
  DFHFCDR  DFHFCFS  DFHFCIN1 DFHFCMT  DFHFCRC2 DFHFCRP  DFHFCRR
  DFHFCSDS DFHFORMS DFHME64  DFHMEDM  DFHMEDUF DFHMEME  DFHMEMPC
  DFHMEMPE DFHMEMPK DFHMPAC  DFHMPACT DFHMPDD  DFHMPDDT DFHMPDE
  DFHMPDM  DFHMPDUF DFHMPFED DFHMPIB  DFHMPIBT DFHMPMO  DFHMPPP
  DFHMPRL  DFHMPSC  DFHMPSCT DFHMPST  DFHMPTRI DFHS2GF  DFHSIB1
  DFHSMGF  DFHSMMF  DFHSMMG  DFHSTNDD DFHXMAB  DFHXMAT  DFHXMCL
  DFHXMCLT DFHXMCLX DFHXMCLY DFHXMDM  DFHXMDU2 DFHXMDUF DFHXMER
  DFHXMERT DFHXMQC  DFHXMQCT DFHXMRSD DFHXMTA  DFHXMTRI DFHXMXE
  DFHXSDM  DFHXSRC
  

Fix information

• Fixed component name

  CICS TS Z/OS V5

• Fixed component ID

  5655Y0400

Applicable component levels

• R000 PSY UI55320

     UP18/04/24 P F804 ­

• R100 PSY UI55321

     UP18/05/01 P F804 ­

Fix is available

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