Index ms slow sql updating

Denny has written several books and dozens of technical articles on SQL Server management and how SQL Server integrates with various other technologies.

As shown in the previous part of this series, inaccurate statistics can degrade SQL Server performance.

If there were no data changes on the table, UPDATE STATISTICS will have no effect. On a table with frequent data changes, statistics old an hour can be obsolete and inaccurate. However, this is the case only for the tables with a small number of records, such as this one.

In this example, we will use the Adventure Works database, the Person. The table contains 19,614 rows and we will insert additional 10,000 records. After updating table statistics, the correct values are shown. The All density value is calculated as 1/total number of distinct rows.

Consider disabling those indexes to see if that improves performance.

Do keep in mind that the sys.dm_db_index_usage_stats dynamic management view is reset to all zeros every time the SQL Server instance is restarted, so don't restart SQL Server then disable everything which hasn't been used.

In addition to that, write changes have to then be made to all 10 data pages (one data page per index) so that the data can be written to the data file as well.

All those writes have to happen before the user transaction can be completed.

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The best thing to do is to review the index usage information from the sys.dm_db_index_usage_stats dynamic management view and find out which indexes haven't been used for seeds, scans or lookups but are being maintained.We described how to work with SQL Server statistics using SQL Server Management Studio options and T-SQL.In this article, we will show how to update SQL Server statistics, what are the updating costs, and when updating is recommended.Disabled indexes can simply be deleted after you are sure that they aren't needed.About the Author Denny Cherry is the owner and principal consultant for Denny Cherry & Associates Consulting and has over a decade of experience working with platforms such as Microsoft SQL Server, Hyper-V, v Sphere and Enterprise Storage solutions.

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