DY47833: SYSTEM HANG DUE TO INFINITE LOOP IN AOM SYSTEM TASK DASD/TAPE ATTENTION INTERRUPT PROCESSING

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• The system is hung (softwait). The AOM system task is in an
  infinite loop. The AOM debug area (in SVA phase IJBAOM,
  eye-catcher 'AOM-DBUG') is flooded with 'At' entries for a
  single device/request.
  With DEBUG ON one of the following messages is repeatedly
  written to the console:
  
  AOMUS08I DEVICE UNAVAILABLE
  AOMUS09I INTERNAL PROCESSING ERROR
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All users of z/VSE.                          *
  ****************************************************************
  * PROBLEM DESCRIPTION: The system is hung (softwait). The AOM  *
  *                      system task is in an infinite loop.     *
  ****************************************************************
  * RECOMMENDATION: Install the PTF for this APAR.               *
  ****************************************************************
  DASD/tape attention interrupts are processed by the AOM system
  task. Either an ATT request based on the template AO#PLICB
  (with AO$F1ATT set) is enqueued to PBXAOMMS or AO$F1ATT is set
  in an existing PLF request awaiting a response.
  
  AOM request processing is terminated early if a request fails
  any of the consistency checks in routine AOMINSVA as follows:
  - internal error
    (DEBUG message "AOMUS09I INTERNAL PROCESSING ERROR") or
  - invalid device status
    (DEBUG message "AOMUS08I DEVICE UNAVAILABLE").
  The return path then erroneously does not distinguish between
  ATT and PLF requests and always returns via routine AOMRCPLF.
  This causes ATT requests to be left enqueued and therefore to
  be processed over and over again (infinite loop).
  
  For instance if a device does have a PBXVCTE of zero the
  routine AOMMPROC causes the request to be processed with
  R4=A(VCTE)=0 and R3=A(PUB)=0 (see label AOMMPATT). This
  triggers the CUU consistency check which results in an internal
  error.
  

Problem conclusion

• Return via AOMRCATT instead of AOMRCPLF when the request is an
  ATT request (without AO$F1PLF set). This causes the request to
  be freed and therefore prevents that it is processed over and
  over again. This effectively causes the attention interrupt to
  be ignored.
  

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:

  UD54379

Modules/Macros

• $IJBAOM
  

Fix information

• Fixed component name

  VSE/AF SVR/BAM

• Fixed component ID

  5686VS606

Applicable component levels

• R62C PSY UD54379

     UP20/08/04 I 1000

Fix is available

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