September 19, 2012 at 2:45 pm
1) How can I check the Fragmentation of the indexes.
2)How the scanDensity and Fragmentation are related?
Thanks
September 19, 2012 at 8:00 pm
In SQL Server 2005 and later version, you can use sys.dm_db_index_physical_stats to query size and fragmentation information for the data and indexes. http://msdn.microsoft.com/zh-cn/library/ms188917.aspx
In SQL Server 2000, you could use DBCC SHOWCONTIG .http://msdn.microsoft.com/en-us/library/ms175008.aspx
The main effect of fragmentation is that it slows down page read-ahead throughput during index scans. This causes slower response times.(When you query a fragmentated tables, SQL engine need scan more pages, after
defragmentation, it will scan less pages which reduce I/O and memory utilization).
September 25, 2012 at 7:11 am
If you have found fragmentation or low scan density and you want to run a daily job to remediate it I would recommend looking into this:
http://ola.hallengren.com/sql-server-index-and-statistics-maintenance.html
There are no special teachers of virtue, because virtue is taught by the whole community.
--Plato
September 28, 2012 at 11:01 am
How are the missing indexes created on the table?
on our Prod server, we see a quite few number of missing indexes created.
September 28, 2012 at 11:08 am
Ola's solution does not do that. Honestly you do not want anything automatically creating missing indexes. If you're referring to what's in the DMV or what the Database Tuning Advisor produces as suggestions you might notice that there is a lot of leading column duplication in their suggestions. You want to analyze the suggestions, determine the weight advantage of each option and maybe even after rolling them up into one covering index, and then test your queries before implementing anything.
There are no special teachers of virtue, because virtue is taught by the whole community.
--Plato
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