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The principle focus of query tuning is to provide reliable summary information about the data to the optimizer. This is done by collecting accurate statistics which are then stored in a synoptic data structure known as an interval histogram. The correct choice of the column and index sets on which Statistics should be collected can help the optimizer generate better query plans, dramatically improving query performance and reduce the collection overhead. It can be difficult to understand how the optimizer uses statistics as well as deciding what statistics are needed without an automated method to help. That automated method is the Teradata Statistics Wizard, which is a client-based GUI interface for obtaining statistics recommendations for particular queries or query workloads that are submitted for analysis.

Teradata Visual Explain adds another dimension to the EXPLAIN modifier by depicting the execution plans of complex SQL statements visually and simply. The graphical view of the statement is displayed as discrete steps showing the flow of data during execution.

However, Visual Explain was using QCD to captured the query execution plan steps in relation tables to generate visual explain for query diagnostic. QCD has performance issues due to the many inserts required in QCD de-normalized tables. DBS has implemented DBQL and QCD XML plan logging for TD 13.10. These enhancements provide additional capabilities to users wishing to tune queries and applications in order to achieve better performance.