IDUG Tech Talk: The ABCs of Filter Factors (aka Selectivity)

Tuning of SQL queries requires understanding why DB2 chose a particular access path and determining whether or not that access path should perform as expected. The key to this is understanding what filter factors are, how they are used by the Optimizer and how to get DB2 to better estimate them (with more statistics, or by telling DB2 what the filter factor is).

oe Geller has been a DB2 consultant since Version 1.2. He’s been a Data Architect, DBA, Data Modeler and Software Engineer, often simultaneously. He feels that the best way to learning one aspect of a system is to work on all aspects. Joe specializes in performance tuning. He once rewrote a Peoplesoft view and improved the query by a factor of 70,000. Joe is the author of two books on database systems – DB2 Performance and Development Guide and IMS Administration, Programming and Data Base Design. Currently Joe is working as a database performance specialist for JPMorgan Chase. Joe is an IBM Champion for Information and is a member of the IDUG Content Committee