Visual Explain Tool

Visual Explain is used to view the access plan for explained SQL statements as a graph. The information in the graph can be used to tune SQL queries for better performance.

An access plan graph shows details of:

• Tables (and their associated columns) and indexes

• Operators (such as table scans, sorts, and joins)

• Table spaces and functions

• Cost (in timerons)

You can use Visual Explain to perform the following tasks:

• View the statistics that were used at the time of optimization. You can compare these statistics to the current catalog statistics to help you determine whether rebinding the package might improve performance.

• Determine whether or not an index was used to access a table. If an index was not used, Visual Explain can help you determine which columns might benefit from being indexed.

• View the effects of performing various types of tuning by comparing the before and after versions of the access plan graph for a query.

• Obtain information about each operation in the access plan, including the total estimated cost and number of rows retrieved.