Defragging Indexes For Beginners

Why we need to defrag indexes

• Fragmented indexes are ineffective• Ineffective indexes are slooooooow

Over to the code….

We are going to:

• Create a database• Create a table • Load some data• Add an index• Fragment the index• Fix the index

Demo...

Which option is best?

• > 5% and < = 30% fragmentationALTER INDEX REORGANIZE

• > 30% fragmentationALTER INDEX REBUILD WITH (ONLINE = ON)

Keep your indexes sweet

• Perform regular maintenance on your database, include index checks/defrags as part of the maintenance task.

• A tool such as Idera’s SQL Defrag Manager could be useful, but it is pricey.

• Write a script and set up a scheduled task to automate your index maintenance.

Conclusion• Reorganize Index

− Peformed online− Does not lock for long periods− Does not block updates or other queries− Best option for fragmentation between 5% and

30%.• Rebuild Index

− Drops and recreates the index− Will give the best defragmentation results− Can be performed online or offline− Best option for fragmentation greater than 30%

• Maintenance− Monitor your index fragmentation− Fix fragmented indexes before they become a

problem

Resources• Click on the Word icon to the right to access the SQL code and

notes used in the practical element of this session.

• Download AdventureWorks2008 DBs for free here: http://tinyurl.com/c6y6a3

• More info on fill factors over at the MSDN site: http://msdn.microsoft.com/en-us/library/aa933139(SQL.80).aspx

• Detailed information on Reorganize and Rebuild: http://msdn.microsoft.com/en-us/library/ms189858(SQL.90).aspx

• Great information on Indexes from Brad McGehee• http://tinyurl.com/mfx8h7

• Maintenance Options:• http://www.idera.com/Products/SQL-Server/SQL-defrag-manager

/• http://msdn.microsoft.com/en-us/library/aa258803(SQL.80).

aspx

Microsoft Office Word Document

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