Index validation is the process of checking to see if the recommended indexes actually improve system performance. Validation does not involve the actual execution of the recommendations, but permits the Teradata Optimizer to use the recommended indexes in the plan generation. If the recommendations are created with a COLLECT STATISTICS option, Index Wizard collects statistics on a sample size and saves them in the QCD. The sampled statistics are used during index validation.
The validation process occurs in a simulated session mode. The index and the required statistics (as indicated by the recommendations) are simulated for the plan generation. Index recommendations are validated on the set of statements that were analyzed. The statements are submitted to the Teradata Database in a “no execute” mode. During validation, the query plans are saved into the specified QCD.
Recommendations for the workload are loaded either from QCD or from a file.
Validation topics include the following: