PH59376: DFHDS0102 SHOWS QR TCB DISPATCH / INTERVAL RATIO ABOVE 100%

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• DFHQRCPU runs on its own L8 TCB. When it calls DFHDSST to
  extract the statistics, get_common_values is called. For both
  the cases where collect stats and reset stats, and for just
  collect stats, the code has extra code to "add on" additional
  time accrued under QR. This subtracts the WAIT_FINISH time from
  the TCB_CURRENT_TIME (both DSTCB fields), to get the additional
  time delta that the QR TCB has been dispatched and doing work
  since it last finished a partition exit suspend to MVS. But if
  the QR TCB was actually asleep in MVS at this moment in time.
  The code assumes the EXTRACT STATISTICS command is issued under
  QR, so QR by definition must be currently dispatched to MVS, and
  not asleep like this. But DFHQRCPU is not on QR, so this
  assumption is wrong. This errornously could add  to the time the
  QR TCB is reported to have been dispatched. Then, when the next
  stats runs and shows a valid value we assume the stats were
  reset as we have "gone down from the previous amount of time
  accrued for QR being dispatched", and we display the wrong ratio
  in the message
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All CICS users.                              *
  ****************************************************************
  * PROBLEM DESCRIPTION: Invalid percentage information          *
  *                      displayed in DFHDS0102 messages.        *
  ****************************************************************
  DFHQRCPU runs periodically and reports the QR TCB's current
  CPU / dispatch ratio, along with its dispatch / interval ratio
  (how "saturated" the QR TCB is; that is, how busy it was over
  the interval between DFHQRCPU reporting periods).
    DFHQRCPU issues an EXTRACT STATISTICS command to return the
  dispatcher domain statistics it requires to perform the
  calculations for these ratios. DFHDSST returns this information.
  It invalidly assumes that it is being called under the QR TCB
  so adds on the additional time since the QR TCB was last
  dispatched by the operating system. However, DFHQRCPU runs under
  an L8 TCB, so this assumption by DFHDSST is incorrect.
    The additional time value results in DFHQRCPU's calculation
  assuming a statistics reset has taken place when it has not, and
  the next DFHDS0102 message can display an invalid value for the
  dispatch / interval ratio - in the customer's case this value
  exceeded 100%.
    DFHQRCPU also has an incorrect calculation when working out
  the remainder for this ratio - the logic uses the remainder of
  a division step, rather than the quotient value. This leads to
  inaccurate values being reported in general.
    DFHQRCPU also fails to correctly detect a genuine statistics
  reset when one has actually taken place.
  

Problem conclusion

• DFHDSST has been changed to only add on the additional time
  value for the QR TCB if it is being driven under the QR TCB
  itself.
    DFHQRCPU now uses the quotient value when calculating the
  remainder of the dispatch / interval ratio. It also correctly
  determines whether a statistics reset has taken place since it
  was last invoked.
  

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:

  UI96987

Modules/Macros

• DFHDSST  DFHQRCPU
  

Fix information

• Fixed component name

  CICS TS Z/OS V6

• Fixed component ID

  5655YA100

Applicable component levels

• R400 PSY UI96987

     UP24/05/22 P F405

Fix is available

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