Page

Page Types

There are several types of database pages:

1. Data Page details how the data is stored inside the data files, database.
2. Index Page contains index entries.
3. Text and Image contains textual and image data.
4. GAM (Global Allocation Map) and SGAM (Shared Global Allocation Map) contain information about whether extents are allocated.
5. PFS (Page Free Space) contains information about the free space available on pages and about page allocation.
6. IAM (Index Allocation Map) contains information about extents used by a table or index.
7. Bulk Changed Map contains the extent information that has been modified by bulk operations since the last BACKUP LOG.
8. Differential Changed Map contains the extent information that has changed since the last BACKUP DATABASE.

Data File Pages

The disk space allocated to data file in SQL Server is logically divided into pages. The pages are numbered sequentially starting with zero. Because every file has its own ID number, page identification requires the page number and the file ID. The first page in each file is a file header and the following few pages contain system information. Database boot page (contains database attributes) is stored in the first log file and in the primary data file.