Data in sql server is stored in Data pages.Pages in a SQL Server data file are numbered sequentially, starting with zero for first page in data file. Each file in a database has a unique file ID number. To uniquely identify a page in a database, both the file ID and the page number are required.
Page size in the sql server is 8kb.That means that sql server have 128 pages in 1MB.Each page begins with a 96-byte header.
Extents :-
- Extents are a collection of eight physically contiguous pages and are used to efficiently manage the pages. All pages are stored in extents.
- This means SQL Server databases have 16 extents per megabyte.
SQL Server has two types of extents :-
- Uniform extents are owned by a single object; all eight pages in the extent can only be used by the owning object.
- Mixed extents are shared by up to eight objects. Each of the eight pages in the extent can be owned by a different object.