In Oracle Database 11g, there's a new tool—SQL performance analyzer—that enables you to replay all your SQL statements before and after any number of changes and compare the results to see the changes' impact. You can gauge the overall impact as well as that on individual SQL statements.

This article demonstrates how to use SQL performance analyzer to gauge the overall impact of creating an index on a column in a sample table and then refreshing the statistics on the table and the index.

Please find complete article at attachment.