Solved

SQL Index Fragmentation?

Posted on 2014-10-27
4
235 Views
Last Modified: 2014-10-27
Hi,

I have some fragmented indexes in SQL 2008 R2.

I have been reindexing them with:

DBCC DBREINDEX

or command like:

alter index ... on dbo... REBUILD

anyway not all indexes seem to reduce in fragmentation to 0.

So I am curious have I got an unreasonable expectation here?

what should I expect the outcome to be? And why might some
not reduce to 0?

btw here is the SQL I am running to work out fragmentation:

declare @current_time as nvarchar(20)

set @current_time = convert(varchar, getdate(), 3) + ' ' + convert(varchar, getdate(), 24)

SELECT @current_time as Timestamp,
DB_NAME(database_id) AS [Database Name], OBJECT_NAME(ps.OBJECT_ID) AS [Object Name],
i.name AS [Index Name], ps.index_id, index_type_desc,
avg_fragmentation_in_percent, fragment_count, page_count
FROM sys.dm_db_index_physical_stats(DB_ID(),NULL, NULL, NULL ,'LIMITED') AS ps
INNER JOIN sys.indexes AS i WITH (NOLOCK)
ON ps.[object_id] = i.[object_id] AND ps.index_id = i.index_id
WHERE database_id = DB_ID()
AND page_count > 1500
ORDER BY OBJECT_NAME(ps.OBJECT_ID), avg_fragmentation_in_percent DESC OPTION (RECOMPILE);

Thanks,

Ward.
0
Comment
Question by:whorsfall
  • 2
  • 2
4 Comments
 
LVL 46

Expert Comment

by:Vitor Montalvão
ID: 40406129
Your script it's only taking in consideration the page count (1500+) but Microsoft's recommendation is to check for fragmentation level. Here's the MSDN article about it where you'll see that a reindex should be performed when fragmentation level between 5% and 30% and a rebuild should be performed when fragmentation's higher than 30%.
0
 

Author Comment

by:whorsfall
ID: 40406204
Hi,

Thanks for that so I can assume after a rebuild then the fragmentation should be 0?

Plus assuming I get all the tables by changing my query.

And what about the command dbcc dbreindex?

Thanks,

Ward
0
 
LVL 46

Accepted Solution

by:
Vitor Montalvão earned 500 total points
ID: 40406218
You can't assume a fragmentation level of 0%. That depends if there's no records changes (INSERT, UPDATE and DELETE) during or immediately after the reindex. But it's almost sure that you can assume a fragmentation lower than 5%.

Don't use DBCC REINDEX because will be deprecated in the next SQL Server version. Use ALTER INDEX instead, with REORGANIZE option for avg_fragmentation_in_percent between 5% and 30% or with REBUILD option for avg_fragmentation_in_percent > 30%.
0
 

Author Comment

by:whorsfall
ID: 40406224
Hi,

Thanks for the clarification that was great :)

Ward
0

Featured Post

Comprehensive Backup Solutions for Microsoft

Acronis protects the complete Microsoft technology stack: Windows Server, Windows PC, laptop and Surface data; Microsoft business applications; Microsoft Hyper-V; Azure VMs; Microsoft Windows Server 2016; Microsoft Exchange 2016 and SQL Server 2016.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Title # Comments Views Activity
Dimension table indexes 8 14
T-SQL--Two Different Totals Even with the Same Concept 6 46
SQL 2008 R2 calc date formula 3 28
SQL VIEW 7 25
Slowly Changing Dimension Transformation component in data task flow is very useful for us to manage and control how data changes in SSIS.
Ever wondered why sometimes your SQL Server is slow or unresponsive with connections spiking up but by the time you go in, all is well? The following article will show you how to install and configure a SQL job that will send you email alerts includ…
Via a live example, show how to extract insert data into a SQL Server database table using the Import/Export option and Bulk Insert.
Viewers will learn how to use the SELECT statement in SQL to return specific rows and columns, with various degrees of sorting and limits in place.

863 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

19 Experts available now in Live!

Get 1:1 Help Now