With the DB2 optimizer, the optimizer is the component of DB2 that determines the access plan to be used. During the preparation (static bind or dynamic prepare) of an SQL statement, the SQL compiler is called on to generate an access plan. The access plan contains the data access strategy, including index usage, sort methods, locking semantics, and join methods. To predict performance or troubleshoot performance problems, we need to understand what the optimizer is doing in order. Here we'll look at the various access paths and components evaluated by the optimizer when determining the plan for data access.

This book contains general information about improving performance for DB2 on
z/OS and specific information about how BMC products help improve performance.