This presentation from the IDUG EMEA 2016 will provide an overview of DB2 LUW statistics and the options to collect them, to help you achieve optimal query performance, with minimal administration effort.
Scenario – your query is performing poorly. You see DB2 picked an access path that is less than optimal. First you make sure there are appropriate indexes. You look to see if the statement is written in a way that enables DB2 to use those indexes. Then you check the Filter Factors of the predicates.