My DB2 UDB articles

1. When We Think That the Optimizer Doesn't Get It Right
Some simple tips to make sure the optimizer makes good decisions for your queries.

http://www.devx.com/ibm/Article/11179/0

2. Essential Facts about Index Covering in DB2 Universal Database
xamples to illustrate cases in which adding a column or two to an index can boost a query's performance by "covering" the columns used in a SELECT statement. The DB2 optimizer is very good in recognizing such situations and can choose a very efficient execution plan.

http://www-128.ibm.com/developerworks/db2/library/techarticle/0303kuznetsov/0303kuznetsov.html

3. Using DB2 UDB OLAP functions
Online analytical processing (OLAP) functions are very flexible and powerful. Using them, you may come up with simple solutions to some problems that would otherwise require either iteration through one or several cursors or recursion. In some other cases it is much easier to write a query using OLAP functions or auxiliary tables than to write an equivalent query not using them.

http://www-128.ibm.com/developerworks/db2/library/techarticle/dm-0401kuznetsov/index.html

4. Using Materialized QueryTables to Speed up Queries in DB2 UDB
Sometimes a simple change in physical database structure dramatically improves query performance. In addition to indexes, DB2 UDB provides you with materialized query tables, which in some cases are more efficient than indexes. This article provides ...

http://www-128.ibm.com/developerworks/db2/library/techarticle/0208kuznetsov/0208kuznetsov.html