Sparse indexing has been around for a number of versions. The history of these on the z/Os side goes back to originally helping with non-correlated subqueries in V4, then star joins in V7, to hashing support of these indexes in V10.
Calisto Zuzarte from IBM explains the ins and outs of writing SQL for performance
I searched for the manual which would explain how to write proper SQL. I never found it and the more I talked to people on which strategy I should follow, the less useful information I seemed to get. The same was true whenever I asked for general rules to decide which index was needed.
Joe Geller discusses some favorite tuning tips for Db2 in this video recorded at IDUG EMEA in Lisbon last month.
When it comes to tuning a query, program, or even an application that most developers are not sure where to begin or what may be causing response time issue(s). This article is here to help!