Understanding the Internals of a Data Page


The data SQL Server logically stores into tables is physically stored on several 8 KB data pages. While there are several types of pages in SQL Server such as Boot page, Page Free Space (PFS), Global Allocation Map (GAM), Index page, and the like, data pages are the core of storage structures such as heaps and indexes.

There are three types of data pages in SQL Server: in-row, row-overflow, and LOB data pages. Knowing the internals of a data page is critical to understanding what happens internally when we change data, how data rows consume space on data pages,