PI23765: DB2 MAY INCORRECTLY SELECT N ACCESS TYPE INSTEAD OF IN ACCESS TYPE ON V11

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• DB2 may select N access type instead of IN access type on V11,
  while the access path with IN access type performs better.
  

Local fix

• N/A
  

Problem summary

• ****************************************************************
  * USERS AFFECTED: All users of DB2 11 for z/OS whose query     *
  *                 contains more than one IN-list predicate.    *
  ****************************************************************
  * PROBLEM DESCRIPTION: DB2 may not choose an efficient         *
  *                      access path utilizing either access     *
  *                      type 'N' or access type 'IN' when the   *
  *                      query contains more than one IN-list    *
  *                      predicate.                              *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  DB2 may not choose an efficient access path utilizing
  either access type 'N' or access type 'IN' when the query
  contains more than one IN-list predicate.
  
  For example,
  
  SELECT *
  FROM T1
  WHERE C1 IN (?, ?)
    AND C2 IN (?, ?)
    AND C3 = ?
    AND C4 = ?
  
  If there is an index defined on T1(C1,C2,C3,C4)  and  the
  index is selected to access T1, the DB2 optimizer may choose
  'N' access type with only 1 matching predicate instead of
  an access path using 'IN' access type with 4 matching
  predicates.
  
  Additional Keywords:
  SQLACCESSPATH SQLPERFORMANCE SQLIN
  

Problem conclusion

• The DB2 optimizer is enhanced to choose the number of matching
  predicates based on cost estimation when there are multiple
  IN list predicates that can be matching.
  

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:

  UI22692

Modules/Macros

•    DSNXOGBM
  

Fix information

• Fixed component name

  DB2 OS/390 & Z/

• Fixed component ID

  5740XYR00

Applicable component levels

• RB10 PSY UI22692

     UP14/11/18 P F411

Fix is available

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