PI27934: WRONG INDEX IS USED DUE TO INCORRECT IMFF ESTIMATION

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• An index provides more matching columns and better index
  matching filter factor than the competing indexes, but not
  selected by optizer due to incorrect matching filter factor.
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: DB2 11 for z/OS users whose queries contain  *
  *                 more than one join predicate.                *
  ****************************************************************
  * PROBLEM DESCRIPTION: DB2 may give an incorrect compound      *
  *                      filter factor for a set of join         *
  *                      predicates. It may lead to an           *
  *                      inefficient access path.                *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  DB2 may give an incorrect compound filter factor for a set of
  join predicates. It may lead to an inefficient access path.
  
  For example,
  
  SELECT *
   FROM  T1, T2
   WHERE T1.C1 = T2.C1
         T1.C2 = T2.C2
  
  There are two join predicates T1.C1 = T2.C1 and T1.C2 = T2.C2
  in the query. DB2 may give an incorrect compound filter factor
  for predicates T1.C1 = T2.C1 and T1.C2 = T2.C2. It may lead to
  an inefficient access path.
  
  ADDITIONAL KEYWORDS:
  
  SQLACCESSPATH  SQLPERFORMANCE  FILTERFACTOR
  

Problem conclusion

• Code is fixed to solve the problem described as above.
  

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:

  UI24820

Modules/Macros

•    DSNXOCCF DSNXOGP
  

Fix information

• Fixed component name

  DB2 OS/390 & Z/

• Fixed component ID

  5740XYR00

Applicable component levels

• RB10 PSY UI24820

     UP15/02/17 P F502

Fix is available

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