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SQL Anywhere 11.0.1 » SQL Anywhere Server - SQL Usage » Monitoring and Improving Database Performance » Improving database performance » Index Consultant


Understanding Index Consultant results

The Index Consultant provides a set of tabs with the results of a given analysis. You can save the results of an analysis for later review.

Summary tab

The Summary tab provides an overview of the analysis, including the number of queries, the number of recommended indexes, the number of pages required for the recommended indexes, and the benefit that the recommended indexes are expected to yield. The benefit number is measured in internal units of cost.

Recommended Indexes tab

The Recommended Indexes tab contains data about each of the recommended indexes. The information provided includes:

  • Clustered   Each table can have at most one clustered index. In some cases, a clustered index can provide significantly more benefit than an unclustered index. See Using clustered indexes.

  • Pages   The estimated number of database pages required to hold the index if you choose to create it. See Table and page sizes.

  • Relative Benefit   A number from one to ten, indicating the estimated overall benefit of creating the specified index. A higher number indicates a greater benefit.

    The relative benefit is computed using an internal algorithm, separately from the Total Cost Benefit column. There are several factors included in estimating the relative benefit that do not appear in the total cost benefit. For example, it can happen that the presence of one index dramatically affects the benefits associated with a second index. In this case, the relative benefit attempts to estimate the separate impact of each index.

    For more information, see Implementing Index Consultant results.

  • Total Benefit   The cost decrease associated with the index, summed over all operations in the tracing session, measured in internal units of cost (the cost model). See How the optimizer works.

  • Update Cost   Adding an index introduces cost, both in additional storage space and in extra work required when data is modified. The Update Cost column is an estimate of the additional maintenance cost associated with an index. It is measured in internal units of cost.

  • Total Cost Benefit   The total benefit minus the update cost associated with the index.

Requests tab

The Requests tab provides a breakdown of the impact of the recommendations for individual requests within the tracing session. The information includes the estimated cost before and after applying the recommended indexes, and the virtual indexes used by the query. A button allows you to view the best execution plan found for the request.

Updates tab

The Updates tab provides a breakdown of the impact of the recommendations.

Unused Indexes tab

The Unused Indexes tab lists indexes that already exist in the database that were not used in the execution of any requests in the tracing session. Only secondary indexes are listed: that is, neither indexes on primary keys and foreign keys nor unique constraints are listed.

Log tab

The Log tab lists activities that have been completed for this analysis.

See also