SQL indexes

We've been having some performance issues with slowness.

In one of the tables I saw some some clustered indexes. When I looked into the properties of the clustered index, I saw an option for fragmentation. I assume that Total fragmentation means 'how fragmented the cluster is' correct?

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Yes, this means that this index is stored on different fragments on your hard disk, which in fact means that your table is stored on different fragments on your hard disk, because an index cluster in SQL-Server is what some other RDBMS call Index-Organized Table, which means that all table is stored on the index, or in other words, table is organized on a B-Tree way, according to the key of the cluster index.

This is also the reason why a table only can have a cluster index.

I would recommend to defrag.

Also, you should investigate which is the SQL which is slow, and look for its query plan (maybe you think it uses the index, and it is not using it).

Hope it helps. Regards.
Aneesh RetnakaranDatabase AdministratorCommented:
put a maintenance solution to reindex/reorganise the indexes .
Lots of us use the maintenance solutions from here  https://ola.hallengren.com/
Scott PletcherSenior DBACommented:
Yes, that index is way too fragmented, but that's a very small table overall and is not likely to cause a big performance hit.

The first thing to do for performance is to make sure that each table has the best clustered index.  You can use the missing index stats and index usage stats to help determine this.  Then determine what nonclustered indexes are needed.  Then, finally, yes, make sure you rebuild or reorganize those indexes as needed later.

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Umair QamarCommented:
less fragmentation is good and fill factor of index should be around 90%.
You should use Brent Ozar's scripts to tune your indexes and other matters related to database.
I am attaching a script in this post. Please find and use it. It's safe.sp_BlitzIndex.sql
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Microsoft SQL Server

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