PH70852: KERNDUMP ABEND0C8 ON AN AHI INSTRUCTION IN DFHKEDOM (BASE CICS/TS 6.1) AT OFFSET X'928'.

APAR status

• Closed as program error.

Error description

• Abend0C8 on an AHI instruction in DFHKEDOM when incrementing the
  KCB_GUARD_COUNT and it contains 7FFFFFFF.  The AHI gets the
  Overflow condition in this situation as the number increments
  from 7FFFFFFF (the largest signed 4-byte positive number) to
  80000000 (the largest signed 4-byte negative number).  That
  overflow condition becomes an abend0C8 when the PSW's
  Fixed-Point Overflow mask is on.  (If the PSW's Fixed-Point
  Overflow mask is not on, the overflow is ignored and everything
  is fine.)
  
  Normally, the PSW's Fixed-Point Overflow mask bit is not on when
  in DFHKEDOM .  So normally, there is no problem when
  KCB_GUARD_COUNT overflows on the AHI.
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All CICS users.                              *
  ****************************************************************
  * PROBLEM DESCRIPTION: CICS abends with KERNDUMP,              *
  *                      caused by an 0C8 abend in DFHKEDOM      *
  ****************************************************************
  If an application turns on the Program Mask bits in the PSW,
  and CICS later needs to obtain a Kernel Stack Segment,
  and the stack segment counter is incremented from
  X'7FFFFFFF' to X'80000000',
  then DFHKEDOM suffers an 0C8 abend
  while processing an AHI (Add Halfword Immediate) instruction.
  Additional Keywords: ABENDS0C8 ABEND0C8 0C8 Fixed Point Overflow
  

Problem conclusion

• CICS has been modified to use an UNSIGNED instruction to
  increment its counter.
  

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:

  UO08761 UO08762 UO08763

Modules/Macros

• DFHKEDOM
  

Fix information

• Fixed component name

  CICS TS Z/OS V6

• Fixed component ID

  5655YA100

Applicable component levels

• R400 PSY UP

     C

• R500 PSY UP

     C

• R600 PSY UP

     C