This document discusses advanced index tuning techniques in SQL Server, including: - Using DMVs (dynamic management views) to passively tune indexes by observing performance and removing or adding indexes. - Active tuning techniques such as avoiding over-application of tuning wizard recommendations and giving indexes smart names for ongoing maintenance. - Using data compression for indexes in SQL Server 2008 to reduce storage requirements. - Addressing database fragmentation as a "silent performance killer" and using online reindexing techniques to defragment indexes without taking tables offline.

1. Advanced Index Tuning
© 2008 Quest Software, Inc. ALL RIGHTS RESERVED.

2. About Me: Brent Ozar
• SQL Server Expert for
Quest Software
• Former SQL DBA
• Managed >80tb SAN,
VMware
• Dot-com-crash
experience
• Specializes in
performance tuning

3. Today’s Agenda
• Passive Tuning: Using DMVs
• Active Tuning: Outsmarting the Wizards
• Compression for Indexes
• The Silent Performance Killer
• Resources and Q&A

4. Passive Tuning with DMVs

5. DMV Tuning Lifecycle
Remove
Indexes
Add
Observe
Indexes

6. Removing Indexes

7. Results

8. Why Are These Different?

9. Our Table: Items

10. Indexes On An “Item” Table
• Index #1:
– UPC_Code
• Index #2:
– SupplierID
• Index #3:
– Category
– QtyInStock
Photo licensed with Creative Commons from:
http://www.flickr.com/photos/revolute/1944742197/

11. Data In The Index
Category Qty in Stock Item ID
Bacon 45 1
Bacon 47 2
Bacon 98 3
Bacon 110 5

12. But When It Changes…
Category Qty in Stock Item ID
Bacon 45 1
Bacon 42 2
Bacon 200 3
Bacon 110 5

13. That’s Why…

14. Adding a Formula Column

15. Our Query

16. A Better Way: Includes
CREATE INDEX
IX_Category_Includes
ON dbo.Items (Category)
INCLUDE (QtyInStock)

17. And When It Changes…
Category Qty in Stock Item ID
Bacon 45 1
Bacon 42 2
Bacon 200 3
Bacon 110 5

18. Query Plan

19. Remember, Never SELECT *

20. Leave a Bread Crumb Trail

21. DMV Tuning Lifecycle
Remove
Indexes
Add
Observe
Indexes

22. Missing Index Query

23. Okay – Now What?

24. When Do We Add More Indexes?

25. DMV Tuning Lifecycle
Remove
Indexes
Add
Observe
Indexes

26. Active Tuning: The Wizards

27. Danger! Danger!

28. The End Result
CREATE NONCLUSTERED INDEX
[_dta_index_Activity_11_1977058079__K1_K4_K7_K5_K3]
ON [dbo].[Activity]
(
[ServerName] ASC,
[ActivityTypeID] ASC,
[StatusTypeID] ASC,
[StartTime] ASC,
[DatabaseID] ASC
) ON [PRIMARY]
GO

29. Rename Each Index
CREATE NONCLUSTERED INDEX
[IX_ServerName_ActivityTypeID_StatusTypeID_StartTime_
DatabaseID] ON [dbo].[Activity]
(
[ServerName] ASC,
[ActivityTypeID] ASC,
[StatusTypeID] ASC,
[StartTime] ASC,
[DatabaseID] ASC
) ON [PRIMARY]
GO

30. Makes Ongoing Tuning Easier

31. Active Tuning Summary
• Don’t just apply the recommendations
• Use smart names
• Look for overlaps
• Take the passive approach first

32. SQL 2008 Data Compression

33. Estimating Compression
• sp_estimate_data_compression_savings
– @schema_name
– @object_name
– @index_id
– @partition_number
– @data_compression

34. Index Compression Drawbacks
• Enterprise, Developer Editions only
• No inheritance, no automation
• Get scripts from www.SQLServerBible.com

35. The Silent Performance Killer

36. Pretend You’re SQL Server
Photo Licensed with Creative Commons From
http://www.flickr.com/photos/quacktaculous/3143079032/

37. Does It Really Matter?
The workload performance increase realized in the
small-scale environment ranged from 60 percent at
the low level of fragmentation to more than 460
percent at the highest level of fragmentation.
The workload performance increased realized for the
large-scale environment ranged from 13 percent at
the low fragmentation level to 40 percent at the
medium fragmentation level.
http://technet.microsoft.com/en-
us/library/cc966523.aspx

38. 13-460% Faster, And…
• No app changes
• No vendor issues
• No testing required
• No guessing on indexes
• No backfires
• Fully supported
• Even recommended!

39. Not All Unicorns and Roses
• Standard Edition:
Offline Only
• Enterprise Edition:
Most Online
• Generates a lot of
transaction logs

40. The Native Solution

41. The Better Way: T-SQL Code

42. Don’t Reinvent The Wheel

43. Resources On The Web
• SQL Server Wiki and Script Library:
SQLServerPedia.com
• Scripts to Enable Compression Fast:
www.SQLServerBible.com
• Index Tuning & Maintenance:
SQLfool.com