OA60848: PREDICTIVE FAILURE ANALYSIS INCREASED PFA* PREFIXED JOBS RUNNINGINCREASED CPU USAGE PFA_COMMON_STORAGE_USAGE

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• At z/OS 2.4, PFA_COMMON_STORAGE_USAGE check may erroneously
  cause dynamic modeling to execute frequently.  When dynamic
  modeling occurs, PFA starts a new address space named PFAn.
  Values PFA utilizes to represent storage that is currently in
  use in common storage are in the wrong order for its data.  It
  is using bytes instead of kilobytes.  This makes PFA think
  current usage is much higher then it actually is.  Additionally,
  the amount of storage free is being reported as 0, when common
  storage is not exhausted.  This causes a PFAn prefixed address
  spaces to run more frequently which the cumulutively increases
  CPU usage for the additional PFAn address spaces executing.
  
  At z/OS 2.3 and z/OS 2.4, the calculated change value is
  incorrect but would not increase the amount dynamic modeling
  occurs.
  
  VERIFICATION STEPS:
  For the incorrect order for filesize (Kilobyte versus Byte) and
  the calculated change value see areas denoted with <--- below.
  1. Enable PFA Debug mode
  f hzsproc,update,check(IBMPFA,PFA_CO*),parm('debug(1)')
  
  2. Allow PFA to run for at least an hour in debug mode.
  
  
  3. Review of PFA zfs data will show a Category for CSA, ECSA,
     SQA, ESQA or a combination CSA+SQA / SQA+ESQA
  
     The actual used now will be in bytes, where the predicted
     values are in Kilobytes Available will be 0.  Category:
     ECSA+ESQA
  
    Adjusted capacity    : 364935
    Prediction           : 252294
    Threshold used       : 7298
    Calculated change    : 18446744073709551590   <----
    Actual used now      : 260639920        <------ (254,531KB)
    Actual when predicted: 254531
    Adjusted prediction  : 254505
    Available            : 0              <------
    Comparison value     : 247207
  
  HIGH CPU
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED:                                              *
  * All users of HBB77B0 and HBB77C0 exploiting the Predictive   *
  * Failure Analysis component.                                  *
  ****************************************************************
  * PROBLEM DESCRIPTION:                                         *
  * When calculating the rate of change there were some cases    *
  * where a value could become negative resulting in an          *
  * incorrect value being used for calculations.                 *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  When calculating the rate of change there were some cases where
  a value could become negative resulting in an incorrect value
  being used for calculations. This incorrect value was then used
  in the calculation for the rate of change resulting in an
  inaccurate rate. There was also a scenario when a collection and
  comparison happened at the same time incorrect values could be
  used for rate of change calculations.
  

Problem conclusion

• The code responsible for the rate of change calculation was
  updated to always return the absolute value so that the rate of
  change is calculated with accurate numbers and correct values
  are used when collections and comparisons happen at the same
  time.
  

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:

  UJ05253 UJ05254

Modules/Macros

• AIRPAFUP AIRPAFRP AIRHMMON AIRHMFCU
  

Fix information

• Fixed component name

  Z/OS PFA

• Fixed component ID

  5752SCPFA

Applicable component levels

• R7C0 PSY UJ05254

     UP21/04/23 P F104

• R7B0 PSY UJ05253

     UP21/04/23 P F104

Fix is available

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