PK82783: V8 OPTIMIZER DO NOT CHOOSE LIST PREFETCH

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• V8 optimizer do not choose List Prefetch
  

Local fix

• N/A
  

Problem summary

• ****************************************************************
  * USERS AFFECTED: For all DB2 for z/OS users who have a query  *
  *                 that may exploit index access with list      *
  *                 prefetch.                                    *
  ****************************************************************
  * PROBLEM DESCRIPTION: For a non-clustered index with good     *
  *                      selectivity, DB2 sometimes may          *
  *                      overestimate the list prefetch plan     *
  *                      cost and therefore not choose this      *
  *                      plan.                                   *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  This APAR adds an I/O cost reduction to the list prefetch plan
  in order to alleviate the problem of overestimated cost when
  the index is estimated to be very selective.  This should help
  DB2 to pick the desirable list prefetch plan for some queries.
  
  Additional Keywords:
  SQLACCESSPATH LISTPREFETCH
  

Problem conclusion

• This APAR will help some of the impacted queries to pick the
  desirable list prefetch plan.
  

Temporary fix

Comments

• ž**** PE10/02/10 FIX IN ERROR. SEE APAR PM07281  FOR DESCRIPTION
  

APAR Information

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

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

  UK46742 UK46743

Modules/Macros

• DSNXOFUN DSNXOGCM DSNXOGCX DSNXOGC3 DSNXOSPJ
  

Fix information

• Fixed component name

  DB2 OS/390 & Z/

• Fixed component ID

  5740XYR00

Applicable component levels

• R810 PSY UK46742

     UP09/08/14 P F908

• R910 PSY UK46743

     UP09/08/14 P F908

Fix is available

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