SQL Server Tips by Robin Schumacher

Unused Indexes

To begin with, it is imperative to know which indexes are not being used for a number of reasons. Indexes take up space, so unused indexes waste storage. Indexes also require maintenance for each DML statement, so there is a performance penalty on tables with many indexes that experience high INSERT, UPDATE and DELETE activity.

With new designs, the DBA may not know what indexes will be used, so the basic standard indexing scheme of primary key indexes, clustered indexes, and indexes on most foreign key columns will need to be performed. If load testing scenarios can be implemented before the first day of production, it could be possible to weed out unused indexes.

So, how can unused indexes be located? The DBA can try the Index Tuning Wizard in SQL Server 7 – 2000 or the Database Tuning Advisor in SQL Server 2005. There are also third party products on the market that will capture and analyze SQL workflow and report on unused indexes. Ambeo is currently one such company.

The above book excerpt is from:

High-Performance SQL Server DBA
Tuning & Optimization Secrets

ISBN: 0-9761573-6-5
Robin Schumacher

 http://www.rampant-books.com/book_2005_2_sql_server_dba.htm