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Index fragmentation Script


Index fragmentation Script

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nkm129
nkm129
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Hi,

Could someone has any script to suit following requirement

Need to create Store Procedure which will first look into sys.dm_db_index_physical_stats view and cretae script for

1) REORGANIZE when avg_fragmentation_in_percent value <30%
2) REBUILD when avg_fragmentation_in_percent value >30%
3) Incase if index is clustered in 2'nd case then create REBUILD TSQL Command for all noncluster index in that table.

It should not automatically run but just need to create a Script with these TSQL Command.

Thanks in advance
Rob Symonds
Rob Symonds
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I'm not sure I understand your request entirely. Are you looking for a script to create the TSQL commands for you to use elsewhere or are you looking for a script to actually execute the commands?

If you are just looking to generate the TSQL, you should be able to adapt this script to your needs by playing with the output in the CASE statement. In other words, you could change:

when stats.avg_fragmentation_in_percent < 30 then 'Reorganize'


to something like
when stats.avg_fragmentation_in_percent < 30 then 'ALTER INDEX ' + i.name + ' REORGANIZE...'



I've read that reorganizing/reindexing doesn't make much difference if the index is in the 5k to 10k page range. So this script doesn't look for anything under 5k pages.


use AdventureWorks

SELECT
stats.object_id AS objectid,
QUOTENAME(o.name) AS objectname,
QUOTENAME(s.name) AS schemaname,
stats.index_id AS indexid,
i.name AS index_name,
stats.partition_number AS partitionnum,
stats.avg_fragmentation_in_percent AS frag,
stats.page_count,
CASE
when stats.avg_fragmentation_in_percent < 30 then 'Reorganize'
when stats.avg_fragmentation_in_percent > 30 then 'Rebuild'
END AS 'action_to_take'
FROM
sys.dm_db_index_physical_stats(DB_ID(), NULL, NULL , NULL, 'LIMITED') as stats,
sys.objects AS o,
sys.schemas AS s,
sys.indexes AS i
WHERE
o.object_id = stats.object_id
AND
s.schema_id = o.schema_id
AND
i.object_id = stats.object_id
AND
i.index_id = stats.index_id
AND
stats.avg_fragmentation_in_percent >= 10.0
AND
stats.page_count >= 5000
AND
stats.index_id > 0
ORDER BY
action_to_take


Ola Hallengren
Ola Hallengren
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I have a stored procedure that could help you with this. It is using the DMV
sys.dm_db_index_physical_stats to dynamically rebuild / reorganize indexes based on the fragmentation levels.
http://ola.hallengren.com/sql-server-index-and-statistics-maintenance.html

Regarding 3) about rebuilding non clustered indexes based on the fragmentation of the clustered index. Is this a best practice? The stored procedure does not support this.

Ola Hallengren
http://ola.hallengren.com
nkm129
nkm129
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Regarding 3) about rebuilding non clustered indexes based on the fragmentation of the clustered index. Is this a best practice? The stored procedure does not support this.

Ola :- If clustered index need to be rebuild then don't we need to rebuild all non-clusted index on same table... I am not sure but i think rebuilding clustered index will not rebuild non-clustered automatically..
nkm129
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Rob Symonds

Thanks for script ..

This work fine but actually I need all ALTER TSQL will be in output so I just copy and then run .

I just modified your script and now in action column I am getting all ALTER Script but it is difficult to take one by one and then run insted of this what I want is that I need all these TSQL Command in one output so i just need to run this once.

SELECT
stats.object_id AS objectid,
QUOTENAME(o.name) AS objectname,
QUOTENAME(s.name) AS schemaname,
stats.index_id AS indexid,
i.name AS index_name,
stats.partition_number AS partitionnum,
stats.avg_fragmentation_in_percent AS frag,
stats.page_count,
CASE
when stats.avg_fragmentation_in_percent < 30 then 'ALTER INDEX ' + i.name + ' ON ' +o.name +' REORGANIZE'

when stats.avg_fragmentation_in_percent > 30 then 'ALTER INDEX ' + i.name + ' ON ' +o.name +' REBUILD'
END AS 'action_to_take'
FROM
sys.dm_db_index_physical_stats(DB_ID(), NULL, NULL , NULL, 'LIMITED') as stats,
sys.objects AS o,
sys.schemas AS s,
sys.indexes AS i
WHERE
o.object_id = stats.object_id
AND
s.schema_id = o.schema_id
AND
i.object_id = stats.object_id
AND
i.index_id = stats.index_id
AND
stats.avg_fragmentation_in_percent > 20.0

AND
stats.index_id > 0
ORDER BY
objectname


Thanks in advance...

example :- I need output like that

ALTER INDEX PK__ACH_TRANSFER_DTL__00551192 ON ACH_TRANSFER_DTLS REBUILD

ALTER INDEX PK__CONFIG_AUDIT_LOG__269AB60B ON CONFIG_AUDIT_LOG REBUILD

ALTER INDEX PK__CUSTOMER_ACCOUNT__0425A276 ON CUSTOMER_ACCOUNT_VER_LOG REBUILD
.... like all ALTER coomand which generated from this will be in output.

Thanks!
Ola Hallengren
Ola Hallengren
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>I am not sure but i think rebuilding clustered index will not rebuild non-clustered automatically..

You're right on this. Please see Books Online.
"Rebuilding a clustered index does not rebuild associated nonclustered indexes unless the keyword ALL is specified."
http://msdn.microsoft.com/en-us/library/ms188388.aspx

>If clustered index need to be rebuild then don't we need to rebuild all non-clusted index on same table

As I understand it we only need to rebuild non clustered indexes if they are fragmented.

Ola Hallengren
http://ola.hallengren.com
nkm129
nkm129
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>As I understand it we only need to rebuild non clustered indexes if they are fragmented.


As what I understand is that Noncluster index will be pointing to cluster key so if we have to reuild Cluster index then we have to rebuild noncluster index also to point correct cluster key value and page.

could you please clarify that what i think is right or it is not necessary to rebuild noncluste index even though cluster inde has been reuild.

Thanks!
Ola Hallengren
Ola Hallengren
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Ken Hendersen has a blog post about this.

"If you think about it, it makes perfect sense—the clustered keys, which are the record locators in the NC indexes, aren’t changed merely because you rebuild the index. All rebuilding the index does is lay the pages back down. The rows may move around on the clustered index pages, but we don’t care because the NC indexes don’t use a RID to reference the data; they use the clustered key and have since SQL Server 7.0. "

http://blogs.msdn.com/khen1234/archive/2007/02/27/does-rebuilding-a-clustered-index-rebuild-nonclustered-indexes.aspx

Ola Hallengren
http://ola.hallengren.com
nkm129
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Ola Hallengren

Thanks Ola.. I was confused about rebuilding indexs..

Could you suggest me any post where I can get info about Cluster and Non cluster index as how they work and how value are stored in non cluster so will be having better understanding about indexes..

Thanks again
Ola Hallengren
Ola Hallengren
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Paul Randal has a good blog post about this.
http://blogs.msdn.com/sqlserverstorageengine/archive/2007/06/07/what-happens-to-non-clustered-indexes-when-the-table-structure-is-changed.aspx

About the index optimization stored procedure it outputs things like this to the output file.

DateTime: 2008-03-05 21:58:59
Command: ALTER INDEX [IX_Address_StateProvinceID] ON
[AdventureWorks].[Person].[Address] REORGANIZE
Comment: IndexType: 2, LOB: 0, PageCount: 1001, Fragmentation: 7.40741
DateTime: 2008-03-05 21:59:10

Please try it out and let me know if you have any questions.
http://ola.hallengren.com/sql-server-index-and-statistics-maintenance.html

Ola Hallengren
http://ola.hallengren.com
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