PH47995: ABEND0C4-04 IN DFSUSE00 OFFSET +X'8B0' DUE TO INVALID CCB LATCH USE ANCHOR.

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• The abend0C4-04 (storage protection exception) occurred at
  DFSUSE00 offset +'8B0'. The real offset was +'8AC'.
  The instruction was CDS (Compare and Double Swap).
  Because Register 5 contains an invalid resource header pointer
   ZERO '00000000'.
  The Register 5 loaded from CCBUSEA(CCB LATCH USE ANCHOR),
  but it was already zero.
  Therefore, Register 0 (000A0000) and Register 1 (000130E1)
  were also invalid address which was loaded by LM R0,R1,0(R5)
  instruction after label USE00710.
  .
  The problem trigger was /DISPLAY CONVERSATION command,
   it was issued via OM(Operations manager).
  .
  From SVC DUMP:
  <> Command flow:
  PROCESS /DISPLAY CONVERSATION command via OM.
    --> SCAN CCB ROUTINE (SCANCCB)
      -->  SCANCCB  (SUBROUTINE TO FIND THE FIRST OR NEXT CCB
             in DFSSUT00
        --> DFSUSE CALL FOR TYPE CCB, it issues the INUSE CALL.
          -->  DFSSUT00+C9C -> DFSUSE FUNC=INUSE --> call
           -->  DFSUSE00 -> SET RESOURCE = INUSE -->
             -->  CDS instruction failed,
              *** 'Abend0C4-04' at DFSUSE00 offset+8AC ***
  .
  <> Module flow:
  SAP AT 2A6259E0 RUN LATCH     FLG-80020004 40008000 DPNO-0033A
                  POST-00000000 ECB-38256078 TYPE-CTL
  DFSOCM00+12/08/16-                                +037E
  DFSOCM30+SP53+1510+12/08/16+14.44                 +02D6
  DFSICLD012/08/1613.26                             +00D4
  DFSIDP8012/08/1615.09                             +019A
  DFSIDP80-SCANCCB                                  +0072
  DFSSCBT0+20161208+14.14+1510                      +0160
  DFSSUT00-12/08/16                                 +07BE
  SUT00USE-12/08/16                                 +01F2
  DFSUSE00+1510+20161208+13.55                      +0B08
  USE06000                                             RETURNED
  .
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED:                                              *
  * All IMS V15 users                                            *
  ****************************************************************
  * PROBLEM DESCRIPTION:                                         *
  * ABEND0C4 in module DFSUSE00+08AC on CDS instruction near     *
  * label USE00712.  R5 is 0.  The save area after DFSUSE00's    *
  * save area shows USE06000 as returned.                        *
  ****************************************************************
  * RECOMMENDATION:                                              *
  * INSTALL CORRECTIVE SERVICE FOR APAR/PTF                      *
  ****************************************************************
  This is a timing issue in module DFSUSE00.  DFSUSE00 was called
  to obtain an INUSE on a CCB (conversation control block).  The
  code in DFSUSE00:
  
   1. Obtains the address of the use header from field CCBUSEA.
   2. Validates the address is not zero (if it is, return
      either RC=12 (for COND=YES callers) or ABENDU0790 SC03
      (for COND=NO callers).
   3. Obtain INUSE serialization on the header
   4. Go to DFSUSE00 exit point (USE00900).
  
  
  At USE00900, just before returning to the caller, the code
  verifies that the address of the use header in CCBUSEA has not
  changed from the address that DFSUSE00 used for the INUSE.  If
  the address is different, then code invokes internal subroutine
  USE06000 to release the INUSE, and then branches back to label
  USE00710 (for INUSE) or USE00510 (for CONN) to re-get the
  serialization on the current header.  This code was added in IMS
  V5 by APAR PQ13091 (V6 FF APAR PQ16061 in the SDCs in current
  DFSUSE00).
  
  This retry code does not re-do step 2 in the sequence shown
  above to test the new header address for zero.  In this case,
  the abending DFSUSE00 call was due to a /DIS CONV command
  (module DFSIDP80).  The conversation represented by the CCB had
  ended between the time DFSUSE00 was called and loaded the
  resource header address and the time it exited and did the exit
  validation check.  The /DIS CONV command runs under the CTL TCB;
  the conversation was OTMA and exited under an OIM TCB.  The
  check found field CCBUSEA was zero (so it was different than it
  was on entry) and retried the INUSE with a resource header
  pointer of zero.  Because of the missing check for 0, DFSUSE00
  abended with an 0C4 trying to get an INUSE at low core location
  0.
  
  While this case involved a CCB and conversational processing,
  the verify / retry logic applies to all block types supported by
  DFSUSE00.
  
  Note that while investigating this problem, it was noted that
  the documentation for ABENDU0790 SC02 and SC03 in the IMS
  manuals are incorrect.  The manuals currently say:
  
    X'002'
      Invalid block type has been specified or the use
      anchor pointer is zero.
  
    X'003'
      The requester did not issue in-use function before
      issuing a lock function.
  
  The statement about "or the use anchor pointer is zero" on the
  X'002' subcode description is incorrect, and should be moved to
  the X'003' description.  The DOC HOLD card included with this
  APAR makes this correction.
  

Problem conclusion

• Code is added after the call to USE06000 to check the new header
  pointer for 0.  If 0, then the same logic as is currently at
  label USE00390 is performed:  If COND=YES, set module return
  code in R15 to return code 12.  If COND=NO, issue ABENDU0790
  RC03.  For the RC 12 case, the exit logic also cleans up the
  CULE entry that had been allocated for the INUSE, since it will
  not be used.
  
  DOC HOLD to correct ABENDU0790 documentation:
  
  In IMS V15 manual Messages and Codes, Volume 3: IMS Abend Codes,
  GC27-6791, Chapter 17. IMS abend codes 0751 ? 0800, for abend
  code 0790 (
  https://www.ibm.com/docs/en/ims/15.3.0?topic=0800-0790 ):  The
  current documentation for the abend subcode in register 15 for
  subcodes X'002' and X'003' is not correct.  The abend subcode
  X'002' description contains the phrase "or the use anchor
  pointer is zero".  This phrase should be moved to subcode
  X'003'.  The corrected text for both subcodes is as follows:
  
    X'002'
      Invalid block type has been specified.
  
    X'003'
      The requester did not issue an in-use function before
      issuing a lock function, or the use anchor pointer is
      zero.
  
  This change applies to all levels of IMS currently supported in
  the IBM Documentation Center.
  

Temporary fix

• *********
  * HIPER *
  *********
  

Comments

APAR Information

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

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

  UI82450

Modules/Macros

• DFSUSE00
  

Fix information

• Fixed component name

  IMS V15

• Fixed component ID

  5635A0600

Applicable component levels

• R500 PSY UI82450

     UP22/09/21 P F209 ¢

Fix is available

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