PH54109: DFHFC0001 ABEND 0C4/AKEA IN DFHFCRS CAUSED BY CORRUPT FCP FREE BUFFER CHAIN

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• Task user storage gets corrupted with VSAM file record data.
  A FCP Free BUFFER chain header has been corrupted with an
  address of task storage.
  .
  The sequence of API commands issued by the application leading
  to the problem is as follows:
  EXEC CICS STARTBROWSE FILE
  EXEC CICS READ_NEXT FILE SET
  EXEC CICS READ FILE SET UPDATE
  EXEC CICS REWRITE FILE
  .
  Then the application issues an EXEC CICS SYNCPOINT ROLLBACK.
  .
  The READ_NEXT command getmains its SET storage and places the
  address in an associated FRTE.
  The READ UPDATE command getmains its SET storage, and places the
  address in an associated FRTE.
  On exit from the REWRITE command, the FRTE for the READ UPDATE
  gets released and the SET storage address now appears in the
  FLAB (flab_setu_control) for the file.
  At this point, there is a SET address for the Browser's
  READ_NEXT in a FRTE and the SET address for the READ UPDATE in
  the flab_setu_control.
  Code in DFHFCFR checks if the buffer address in the FRTE is
  different to the SET address in the FLAB.
  If so, then the FRTE SET address is placed on the Free Buffer
  chain. This is incorrect, the address in the FRTE is task
  storage and not from the FCP_256 subpool.
  
  The free buffer chain now contains a storage address that does
  not belong to file control.
  Consequently, when file control needs a SET storage address, it
  takes the next buffer from the free buffer chain causing
  symptoms such as storage violations, abends in file control and
  abends in VSAM.
  Additional symptoms:
  Storage Violations SM0102
  IGW400I ABEND request GET with options 22870000
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All CICS users.                              *
  ****************************************************************
  * PROBLEM DESCRIPTION: An FCP Free BUFFER chain header has     *
  *                      been corrupted with an address of task  *
  *                      storage when preparing to back out a    *
  *                      FRTE for a browse operation.            *
  ****************************************************************
  An EXEC CICS SYNCPOINT ROLLBACK command issued after the
  following sequence of File Control commands caused CICS to place
  the address of task storage (FCSS SET storage used by file
  control) onto the head of the buffer free chain.
  
  EXEC CICS STARTBR FILE
  EXEC CICS READ_NEXT FILE SET
  EXEC CICS READ FILE UPDATE SET
  EXEC CICS REWRITE FILE
  
  Later, when File Control needs a SET storage address and takes
  the address from the head of the buffer free chain,  it may
  cause symptoms such as storage violations, abends in file
  control and abends in VSAM.
  

Problem conclusion

• DFHFCFR has been changed to not place the frt_data_buffer
  address onto the free buffer chain when preparing to back
  out a FRTE for a browse operation.
  

Temporary fix

Comments

APAR Information

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

  PH51344

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

  UI92552 UI92553

Modules/Macros

• DFHFCFR
  

Fix information

• Fixed component name

  CICS TS Z/OS V5

• Fixed component ID

  5655Y0400

Applicable component levels

• R100 PSY UI92553

     UP23/07/04 I 1000

• R200 PSY UI92552

     UP23/07/04 I 1000

Fix is available

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