SQL and Access Paths › Read Mechanisms › Index Lookaside

Index Lookaside

Index lookaside is a performance enhancer that is active only after an initial access to an index. For repeated probes of an index, DB2 checks the most current index leaf page to see if the key is found on that page. If DB2 finds the key, DB2 does not read from the root page of the index down to the leaf page, but it uses the values from the leaf page. This method can affect performance because getpage operations and I/Os can be avoided.

Index lookaside depends on the query reading index data in a predictable pattern. This happens for transactions that are accessing the index using a common cluster with other tables. Index lookaside is dependent on the RELEASE(DEALLOCATE) bind parameter.