PH48590: A LOOP OCCURS DURING THE IIDR/DBCTL TERMINATION PROCESS.

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• A loop occurred during the IIDR/DBCTL termination process.
  .
  The loop was encountered at PC 1402 IWMMDELE call from
  DFSV4200 + 2A42. (A workload manager performance block
  (WLM PB) delete call ( IWMMDELE ) issue to delete a PB)
  It was due to the PTE (Pool Table Entry) pointer address
  
  
  
  which was already chained was passed as the next pointer
  wrongly
  .
  <> Module flow: DFSDASD0/PM91054/UK96502 +178 :
                     IMSAUTH FUNC=WLM_PBPOOL,LIST=(R4)
  .
   +--> DFSV4200/PI53191/UI37443+2A42 :
   |     DFSWLML ENVIRON=PBPOOL,PARM=(R3),PBTKN=IWLME_PBTKN
   |     --> IWMMDELE MONTKN=&PBTKN,MF=(E,&PARM,)
   |        --> IWMI2LPA+01DB98 IN EXTENDED PLPA (LPA: IWMX2DEL02)
   |                        |
   |                        |
   |                        V
   |------------------------+
        **** LOOP *****
  IWLME_NEXT (Table entry chain) pointer back to the previous one
  .
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED:                                              *
  * All users of IMS v15 CCTL Open Thread, ODBA, or ODBM RRS=Y   *
  ****************************************************************
  * PROBLEM DESCRIPTION:                                         *
  * When IIDR (IBM Data Replication) is active, looping may      *
  * occur during DBCTL shutdown or at other times.               *
  * ** NOTE ** This issue is not specific to IIDR, and could     *
  * occur in these environments:                                 *
  * CICS users with Threadsafe enable for IMS threads, ODBM      *
  * users with RRS=Y specified, and ODBA users.                  *
  *                                                              *
  ****************************************************************
  * RECOMMENDATION:                                              *
  * INSTALL CORRECTIVE SERVICE FOR APAR/PTF.                     *
  ****************************************************************
  When IIDR using CCTL Open Thread protocol is active, queues of
  available and free WLM Performance Blocks are maintained.
  Pointers to the queues, along with a count of available queue
  elements, is maintained in the DFSWLMPP block.  Whenever a PB is
  added or removed from one of the queues, this interaction is
  serialized using the CDS instruction as multiple threads may be
  manipulating the queue at the same time.  The code is written in
  a way that assumes that if the address of the first PB on the
  queue is unchanged, and the number of queue elements is
  unchanged, then the queue itself is unchanged.  This is not
  actually true, as in the following example:
  
  1.  Remove element A from the queue
  2.  Remove element B from the queue
  3.  Return element C to the queue
  4.  Return element A to the queue
  
  If this, or something similar, occurs, the serialization may
  fail, and the chain of PBs could become corrupted in a way that
  creates a loop.
  

Problem conclusion

• DFSV4200, DFSDASS0 and DFSDASP0 are changed to only increment
  the count fields of IWLMH_AVALPBQ and IWLMH_FREEPTQ ensuring
  only unique values are used in the update (CDS instruction) of
  the respective fields. A new field has been added to DFSWLMPP to
  track the counts of both available and free PTE queues.
  

Temporary fix

Comments

APAR Information

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

  PH47381

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

  UI82346

Modules/Macros

• DFSDASS0 DFSWLMPP DFSDASP0 DFSV4200 DFSPRRA0
  

Fix information

• Fixed component name

  IMS V15

• Fixed component ID

  5635A0600

Applicable component levels

• R500 PSY UI82346

     UP22/09/10 P F209

Fix is available

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