Call now: (800) 766-1884  


 SQL Server Tips
 SQL Server Training

 SQL Server Consulting
 SQL Server Support
 SQL Server Remote DBA

 SQL Server Scripts
 Scripts Menu




  SQL Server Tips by Gama and Naughter


Pages and Extents


SQL Server stores data in blocks of 8 Kb called Pages and eight contiguous extents are the basic unit of storage for tables and indexes, called Extents. There are two types of extents:  

Uniform extents - the entire extent contains data from one table.


Mixed extents - the extent contains data from two to eight different tables. This is the case of either tables with less than eight pages or the last pages from a table with a total number of pages multiple of eight.

Data Pages are pages that contain data from tables, there are two ways to organize such pages: 

Clustered tables - tables with one clustered index, the pages are linked in a doubly-linked list using the index as a key and the index is stored as a B-tree structure. Indexed views have an identical structure as Clustered tables.


Heaps - tables with no clustered index, the data pages are stored in no particular order and not linked.


Non-clustered indexes have a B-tree index structure but the data pages are stored in no particular order.

The above book excerpt is from:

Super SQL Server Systems
Turbocharge Database Performance with C++ External Procedures

ISBN: 0-9761573-2-2
Joseph Gama, P. J. Naughter


Burleson Consulting Remote DB Administration







Burleson is the America's Team

Note: The pages on this site were created as a support and training reference for use by our staff of DBA consultants.  If you find it confusing, please exit this page.

Errata?  SQL Server technology is changing and we strive to update our SQL Server support information.  If you find an error or have a suggestion for improving our content, we would appreciate your feedback.  Just  e-mail:and include the URL for the page.

Burleson Consulting
SQL Server database support


Copyright 1996 -  2013 by Vaaltech Web Services. All rights reserved.

Hit Counter