1. Understanding the Data Page Structure Sathya Nekkanti Senior Manager/Database Architect

2. 2 Agenda  Data compression  Row compression  Page compression  Structure of the data  Sparse columns  Problems  Alternative solutions  Structure of the data  Q&A

3. 3 Background Information What are records? What are pages? What are extents? What is a heap? What is a clustered index? What is a non-clustered index?

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7. 7 Page A page is 8KB. 1024 bytes X 8KB = 8192 Bytes. Header is 96 Bytes Row offset is 36 Bytes Total 132 Bytes So, 8192 Bytes - 132 Bytes = 8060 Bytes. Each page has 7 bytes of over head So 8060-7 = 8053 is max we can store in any single page.

8. 8 Page structure

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10. 10 Data Compression: Row Compression  Lowest Level of compression  Everything to variable data type  Examples

11. 11 Data Compression: Page Compression Prefix Compression

12. 12 Data Compression: Dictionary compression

13. 13 Sparse Columns: Problems  Heterogeneous data, How to handle

14. 14 Sparse Columns: Alternative Solutions  Name/Value Pair  Normalized tables  XML Bag  Blob

15. 15 Sparse Columns: Regular Row Structure

16. 16 Compressed Row Structure

17. 17 I.Sparse columns Row Structure

18. Questions? sathya@fncinc.com sathya@fncinc.com