PK62804: UTILIZE SYSCOLSTATS TO ENHANCE THE FILTER FACTOR ESTIMATION FOR BETWEEN PREDICATES

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• Utilize SYSCOLSTATS to enhance the filter factor estimation for
  between predicates
  

Local fix

• n/a
  

Problem summary

• ****************************************************************
  * USERS AFFECTED: All DB2 for z/OS users using range or        *
  *                 BETWEEN predicates in queries.               *
  ****************************************************************
  * PROBLEM DESCRIPTION: Sometimes an inefficient access         *
  *                      path is chosen due to inaccurate        *
  *                      filter factor estimation of             *
  *                      range or BETWEEN predicates.            *
  *                                                              *
  *                      The use of SYSCOLSTATS statistics       *
  *                      can enhance the filter factor           *
  *                      estimation of range / BETWEEN           *
  *                      predicates.                             *
  *                                                              *
  *                      SQLBETWEEN SQLLT SQLGT                  *
  *                      SQLACCESSPATH SQLSTATS                  *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  The use of statistics in SYSIBM.SYSCOLSTATS can enhance the
  filter factor estimation of range and BETWEEN predicates,
  which can result in a better access path selection.
  

Problem conclusion

• PK62804 will use SYSCOLSTATS to enhance the filter factor
  estimation of range and BETWEEN predicates, which may result
  in a change in access path.  While the majority of such
  queries could see an improvement in access path, a small
  number of queries could experience somewhat slower
  query performance.
  

Temporary fix

Comments

• ž**** PE09/01/29 FIX IN ERROR. SEE APAR PK79597  FOR DESCRIPTION
  ž**** PE09/07/27 FIX IN ERROR. SEE APAR PK90935  FOR DESCRIPTION
  

APAR Information

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

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

  UK38708 UK38709

Modules/Macros

• DSNDOPCA DSNXCAT  DSNXOCN  DSNXODF  DSNXODFB
  DSNXODFR DSNXOFUN DSNXOLCM DSNXOLFN DSNXOPRS
  

Fix information

• Fixed component name

  DB2 OS/390 & Z/

• Fixed component ID

  5740XYR00

Applicable component levels

• R810 PSY UK38708

     UP08/08/21 P F808

• R910 PSY UK38709

     UP08/08/21 P F808

Fix is available

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