Predicate Analysis

SQL/CA is more than an automated EXPLAIN tool. Its predicate analysis function examines the application's SQL for adherence to the performance rules described in the IBM manual Performance Tuning Handbook (SH09-8111-00). If a statement violates one of these rules, it is flagged with an appropriate message.

Some examples of rules enforced (42 in total):

- the statement should not update a primary indexing column
- the predicate should not use expressions on indexing columns
- the predicate should observe the datatype and datalength compatibility rules
- the operators used in the predicate should allow for selective index access
- the statement predicate should be "sargable" (executable by the DBSS component of DB2/VM)
- leading columns of a multicolumn index should not be omitted

A rule violation results in a warning message. These messages can be searched in an online Glossary, which describes the detected performance exposure in full detail and suggests corrective action. The Glossary also explains the rules governing the evaluation of the statement predicate.