2. Vinod Kumar M
Technology Evangelist – DB and BI
Microsoft Corporation
www.ExtremeExperts.com

3. Session Objectives And Takeaways
Session Objectives
Why data compression?
Describe data compression in SQL Server
Describe Space/Performance trade-offs
Key Takeaways
Can reduce size of a database significantly
Easy to enable/disable
No application changes
Performance gains

4. Agenda
What is the problem?
Solution
Compression in SQL Server 2008

5. Problem
Large Database
Storage Cost
Workload Performance
Manageability Cost
Backup/Recovery

6. Solution
Reduce the size of the database
Reduce the information stored
Compress the data
Compress the data file
No benefit in-memory
Need to compress larger chunks, does not scale
for random access
Store data efficiently in the row/page
(+) More data can fit in memory
(+) Better Performance for I/O bound workload
(-) Performance degradation for CPU bound workload

7. Agenda
What is the problem?
Solution
Compression in SQL Server 2008

8. Compression in SQL Server
SQL Server 2008
ROW and PAGE compression
Backup Compression
Two key changes
Efficient storage of data within
row (both for data and index)
Reduce Data Redundancy on the page

9. Efficient Storage in the ROW
Variable Length Encoding (new row format)
4-byte integer
SQL2005 0 0 0 1 4 bytes
SQL2008 1
(compression enabled)
Special Handling of NULL and 0s
CHAR data type storage optimization

10. Reduce Data Redundancy:
Column Prefix
Factor out common prefix from the same
column across all rows on the page
Store these ‘prefix’ values once and then
reference them from respective columns
Example:
Student (Name VARCHAR (10),
ID INT,
CODE VARBINARY(3))

11. Column Prefix
Page Header
Lambert 5000000 NULL
4 0x5B8D80
5 20x41 0x41AABB
20x42 0x5CAABB
20x43 0x9A4041
0x112233

12. Reduce Data Redundancy:
Page Dictionary
Find repeating values across all
columns on all the rows on the page
Store these values in a dictionary once and
reference them from respective columns

13. Page Dictionary
Page Header
Lambert 5000000 NULL Column prefix
Page Dictionary
4 0x5B8D80
1
5 20x41 0x41AABB
20x42 0x5CAABB
0 20x43 0x9A4041
0 1 0x112233

14. Enabling Compression
Enterprise Edition only
Types of data compressions
ROW
Stores fixed length values as variable length
Superset of vardecimal storage format
Row metadata optimized
BLOB/LOB is not ROW compressed
PAGE (includes ROW)
Column Prefix
Dictionary
Only in-row BLOB/LOB can potentially benefit from PAGE
compression

15. Enabling Compression
Examples
Unpartitioned table
Index
Index Index
Uncompressed
Table
Table
PAGE Compressed

16. Enabling Compression
Examples
Latest partition uncompressed
Uncompressed
PAGE Compressed
ROW Compressed
Jan-Mar Apr-June July-Sept Oct-Dec

17. Data Compression TSQL Example
CREATE TABLE T (c1 int, c2 char(2000) )
WITH (DATA_COMPRESSION = ROW)
CREATE TABLE T_Part (c1 int, c2 char(2000) )
ON somePartScheme (c1)
WITH
(DATA_COMPRESSION = PAGE ON PARTITIONS (1-7),
DATA_COMPRESSION = NONE ON PARTITIONS (8) )
ALTER INDEX CI ON T REBUILD
WITH (DATA_COMPRESSION=PAGE)
ALTER INDEX CI ON T REBUILD PARTITION = 3
WITH (DATA_COMPRESSION=PAGE)

18. Enabling Compression…
Estimate space savings
sp_estimate_data_compression_savings
Space savings depend upon
Schema
Data Distribution

19. Let us estimate ….

20. DML Operations
INSERT (PAGE Compressed)
PAGE Compressed
ROW Compressed
Header Header
CI structure

21. Table And PAGE Compression
Uncompressed
PAGE Compressed
ROW Compressed

22. Btree And PAGE Compression
Uncompressed
PAGE Compressed
ROOT ROW Compressed
INTERNAL INTERNAL INTERNAL INTERNAL
LEAF LEAF LEAF LEAF

23. Impact Of Data Compression
Application
No changes needed in the application
Application throughput increase if I/O bound
Utilities
All Database Utilities (e.g.
Backup, Index, DBCC) fully supported
Gains if I/O bound

24. Supportability
DBCC PAGE enhanced
New Perfmon counters
Page Compression attempts/sec
Page Compressed/sec
New columns in DMVs
sys.db_index_physical_stats
compressed_pages_count
sys.db_index_operational_stats
Page_compression_success_count
Page_compression_attempt_count

26. Summary – Compression
Can reduce size of database significantly
Lower total cost of ownership (TCO)
Easy to enable/disable
No application changes
Performance gains

29. Related Content
Breakout Sessions (session codes and titles)
Interactive Theater Sessions (session codes and titles)
Hands-on Labs (session codes and titles)
Hands-on Labs (session codes and titles)

30. Track Resources
Resource 1
Resource 2
Resource 3
Resource 4

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The information herein is for informational purposes only and represents the current view of Microsoft Corporation as of the date of this presentation. Because Microsoft must respond to changing market conditions, it should
not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information provided after the date of this presentation. MICROSOFT MAKES NO WARRANTIES, EXPRESS,
IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.