IC77195: OPTIMIZER UNDERESTIMATES THE COST OF SORT OPERATIONS FOR WIDE RESULT SETS

APAR status

• Closed as program error.

Error description

• Optimizer underestimates cost of the sort operation for wide
  result sets.  As a result, the wrong execution plan is used:
  sequential scan and sort, instead of index path.
  

Local fix

• Force index path with +INDEX optimizer directive
  

Problem summary

• ****************************************************************
  * USERS AFFECTED:                                              *
  * some order by/group by query might use sequential scan       *
  * instead of index scan                                        *
  ****************************************************************
  * PROBLEM DESCRIPTION:                                         *
  * Slow performance might be seen by customer.                  *
  ****************************************************************
  * RECOMMENDATION:                                              *
  * Upgrade to 11.50.xC10 when available.                        *
  ****************************************************************
  

Problem conclusion

• Fixed in 11.50.xC10.
  

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:

Fix information

• Fixed component name

  INFORMIX SERVER

• Fixed component ID

  5725A3900

Applicable component levels

• RA10 PSN

     UP

• RA10 PSY

     UP

• RB10 PSN

     UP

• RB10 PSY

     UP

• RB50 PSN

     UP

• RB50 PSY

     UP

• RB70 PSN

     UP

• RB70 PSY

     UP