11 Feb 2011

MS SQL Server - index fragmentation

Sometimes it doesn’t make sense to rebuild all of your indexes as part of a maintenance plan. You may have mirroring running with large db tables, and your indexes may be several GB. As part of your maintenance schedule, I recommend manually finding fragmented indexes and rebuilding them yourself (or scripting this)

To do this you, you need to locate the indexes – anything over 50% can be considered a problem.

SELECT ps.database_id, ps.OBJECT_ID,
ps.index_id, b.name,
ps.avg_fragmentation_in_percent
FROM sys.dm_db_index_physical_stats (DB_ID(), NULL, NULL, NULL, NULL) AS ps
INNER JOIN sys.indexes AS b ON ps.OBJECT_ID = b.OBJECT_ID
AND ps.index_id = b.index_id
WHERE ps.database_id = DB_ID()
ORDER BY ps.OBJECT_ID
GO

And then defrag those indexes

DBCC IndexDefrag ('DBNAME','TABLENAME','INDEXNAME' )

http://msdn.microsoft.com/en-us/library/aa258286(SQL.80).aspx

or a full rebuild with

DBCC DBREINDEX ('dbname.ns.tablename','INDEXNAME' )

http://msdn.microsoft.com/en-us/library/aa258828(SQL.80).aspx