One of the most important factors in DB2 application performance is the index design. Poor index usage can ruin the application’s performance. Deciding which columns need indexing, and the order of concatenated keys, is a difficult task. Often it is pure guesswork, based on assumptions and the presence of certain columns in SQL.
Index analysis is a time-consuming and daunting task since it calls for reviewing individual SQL of an application for predicate usage and simultaneously take business priorities into account. A time intensive process because all applications with reference to the target table being indexed have to be reviewed and weighted accordingly. Typically, only experienced DBAs have the skills necessary to design indexes for large applications manually.
When many thousands of queries are involved, an automated Index Administrator system is the only way of ensuring smart indexes.