Validating an index datinghj ru
How can you tell when an index would benefit from being rebuilt?
There are two Oracle views that provide index statistics, DBA_INDEXES and INDEX_STATS.
(listings 8-3 through 8-8) In operational use, the unbalanced index report would be run whenever the DBA suspects that update activity may have unbalanced the indexes.
listing 8.3 The SQL*Plus script to generate the report for index_id1The main driver routine for reporting index_stats Rem © 1997 by Donald K.
Recall that the goal of partitioning clustering algorithms (Part @ref(partitioning-clustering)) is to split the data set into clusters of objects, such that: In this section, we’ll describe the two commonly used indices for assessing the goodness of clustering: the silhouette width and the Dunn index.
Unfortunately, the DBA_INDEXES was designed to provide information to the cost-based SQL optimizer.
Generally, clustering validation statistics can be categorized into 3 classes In this chapter, we start by describing the different methods for clustering validation.
Next, we’ll demonstrate how to compare the quality of clustering results obtained with different clustering algorithms.
The SQL in listing 8.3 will perform an Oracle analyze index xxx validate structure for each index in the schema and report of the resulting values in the Oracle index_stats.
Note: Running id1will invoke id2through id5automatically producing the unbalanced index report.