Index clustering factor oracle 11g download

Oracle 11g introduced online segment shrink functionality to defragment. On clustering factor and validating keys oracle magazine. Oracle database the index clustering factor statistics gerardnico. Pdf the bitmap index advantages on the data warehouses. But when i rebuilt the index clustering factor was still same. In short, the index clustering factor is a measure of how many ios the database would perform if it were to read. The clustering factor is a number which represent the degree to which data is randomly distributed in a table as compared to the indexed column. The clustering factor is useful as a rough measure of the number of ios required to read an entire table by means of an index. In order to change the clustering factor of an existing index, you need to reorg the table data block. Indexes and indexorganized tables 11g release 2 11. Standard edition, standard edition one, and enterprise edition. To improve the index clustering factor, data in the table needs to be. This index quality is based on clustering factor divide clustering factor by number of rowsis excellent, 20% is poor.

Strohm, 2007 oracle database concepts 11g,oracle, redwood city,ca 94065, 2007. Clustering factor and blocks used for bitmap index on grade column. This column has small rows, large blocks, and a low clustering factor. Simply, reorging an existing index, doesnt help in changing the clustering factor. The more order that exists in row storage for this value, the lower the clustering factor. Oracle database 9i, 10g, and 11g programming techniques and solutions, second edition. In simple terms it is the number of block switches while reading a table using an index. Oracle gives following execution plan for the sql at time of writing, tested on all major versions from 10. I want to add the actual percentage sometimebecause oracle could use the index on a poor rating if the clustering factor percent is close to 20%. I created the following table and index to see the clustering factor, and i have a few questions. If the clustering factor is high, then oracle database performs a relatively high number of ios during a large index range scan. High index clustering factor is popular problem in sql world. Index clustering factor and oracle toad world blog.

It is an important statistics which play important. In this case, it is unlikely that index entries in the same leaf block point to rows in the same data blocks. A table with a high clustering factor is outofsequence. There is quite the scenario that the oracle costbased optimizer cbo uses when deciding when to use indexes to process your sql. How oracle index clustering factor is calculated techgoeasy. In the realworld, many oracle database use the same index for the vast majority of queries. I just stumbled upon this bug reference on my oracle support. If the clustering factor is greater than the number of blocks in the index, then the index is out of balance due to a large volume of insert and delete operations. Impact of clustering factor on sql statements in oracle 11g. Defragmentation can degrade query performance simple talk. The clustering factor is a measure of the orderedness of an index in comparison to the table that it is based on.