PM00786: HUNG TRANSACTIONS USING DOCUMENT HANDLER WAITING ON DHLOCK. TASK ABENDS AKEC RUNAWAY TIGHT LOOP IN DFHDHPU

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• You are running CICS transaction server 3.1 and your application
  has issued an 'exec cics document create' command.  You notice
  transactions hang as well as other abend AKEC  which means:
  The kernel (KE) domain has detected runaway.
  Eventually, you cancel the region to resolve the problem.
  A dump from the AKEC showed a tight loop in module DFHDHPU
  between offsets x'68A' and x'6B4'.  Code is trying to chain
  through Document Control Records- or DCR's.  This chain is
  
  corrupt and it happens that we come to an address where the
  next pointer happens to point to itself- causing the loop.
  Looking at the Document Handler Anchor Block, (DHA) offset x'90'
  should point to the first Document Anchor block (DOA) for a task
  but instead points into the DHA.  So this forward pointer
  indicates there are no DOA's but we can tell from the backward
  pointer at offset x'94', that there are some.
  addtional symptoms:  DHA_FIRST_DOA DOA_FIRST_DCR DOA_LAST_DCR
  hang hung looping. Exception trace entry:
  *EXC* - RECOVERY_ENTERED - FUNCTION(CREATE_DOCUMENT)
          TEMPLATE_BUFFER(2C60EBD8 , 000000BA)
  KIXREVEPH
  This problem was also encountered when an HTB in current use had
  previously been a DOA.  Due to the problem described earlier,
  the integrity of the Document Handler Anchor Block and related
  DOAs was compromised, and storage locations in the newly minted
  HTB were still referenced.  One field in the HTB contained the
  address of a DOA, and the subsequent FREEMAIN attempt on the
  address resulted in a mismatch between the freeing subpool
  (PGHTB) and owning subpool (SMSHRC31).  This resulted in an
  exception trace entry and message DFHSM0002.
  .
  DFHPGHM RELEASE_CURRENT_HTB FREEMAIN_RSA FREEMAIN_QUICKCELL QPH
  SM 030E SMGF  *EXC* - Quickcell_freemain_invalid_QPH -
             FUNCTION(FREEMAIN) SUBPOOL_TOKEN(5529F2F0 , 0000005D)
             ADDRESS(277B4000) REMARK(HMRSA) LOCK_POOL(YES)
             LMLM_ADDRESS(24110298)
  SM0002 DFHDOA DFHPG
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All CICS users.                              *
  ****************************************************************
  * PROBLEM DESCRIPTION: An abend (AKEC) has occurred due to     *
  *                      a loop in DFHDHPU when issuing EXEC     *
  *                      CICS DOCUMENT CREATE.                   *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  Customer runs multiple transactions in CICS, some of
  which have issued the EXEC CICS DOCUMENT CREATE command and
  specified the TEMPLATE option.
  
  DFHDHDH handles the document create request.  It creates a
  document anchor block (DOA) and a document control record (DCR)
  for a new document.  DFHDHDH saves the document token in the
  DCR.  The DCR is stored in a chain anchored by the DOA.
  
  DFHDHDH then calls DFHDHPU to create a document template.
  Using the address of DOA, DFHDHPU locates the DCR chain.
  It loops through the chain to locate the DCR that holds the
  the current document token.  However the DCR chain is corrupted.
  DFHDHPU goes into an infinite loop.  A transaction eventually
  abends AKEC.
  
  The CICS recovery manager calls DFHDHRM to carry out backout
  processing.  Document handler is made threadsafe since CICS
  TS 2.3.  However DFHDHRM is not threadsafe while cleaning up
  document blocks such as DOA.  This allows another transaction
  to add a DOA at the same time by issuing EXEC CICS DOCUMENT
  CREATE.  This causes the AKEC and transactions to hang.
  

Problem conclusion

• DFHDHRM has been changed to be threadsafe by obtaining
  the DHLOCK.
  
  The CICS Transaction Server for z/OS, Trace Entries Manual,
  Version 4 Release 1, SC34-7013-00, Chapter 8. Document
  handler trace points needs to be updated to add the following
  trace entries into table 128. Document handler trace points.
  
  Point ID Module  Lvl Type                     Data
  DH 0309  DFHDHRM Exc Get exclusive lock error 1 DFHRMRO
                                                  parameter list
  
  DH 030A  DFHDHRM Exc Release exclusive lock   1 DFHRMRO
                       error                      parameter list
  
  DH 030B  DFHDHRM Exc Recovery release lock    1 DFHRMRO
                       error                      parameter list
  

Temporary fix

• *********
              * HIPER *
              *********
  FIX AVAILABLE BY PTF ONLY
  

Comments

APAR Information

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

  PK96130

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

  UK52341

Modules/Macros

• DESDHAN  DESDHRM  DESDHTRI DFHDHANC DFHDHAND
  DFHDHDCC DFHDHDCD DFHDHRM  DFHDHTRI
  

Fix information

• Fixed component name

  CICS TS Z/OS V4

• Fixed component ID

  5655S9700

Applicable component levels

• R600 PSY UK52341

     UP09/12/01 P F911

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.