Category: SQL Server Internals

• The GAM Interval and GAM Extents

  

  2014-04-09 - General, Series, SQL Server Internals, Storage Wednesday

  What is a GAM extent in SQL Server? What is a GAM Interval and how big is it really? Read on now to get the answers to these questions and see why a GAM interval is not 64000 extents.

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• The Index Allocation Map (IAM)

  

  2014-04-02 - General, Series, SQL Server Internals, Storage Wednesday

  SQL Server tracks the pages that belong to an allocation unit through special index allocation map pages, also called IAM pages. Each IAM page covers a single GAM-interval of the database file. All IAM pages of a single allocation unit together build an IAM-chain. Read on to find out more.

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• The Allocation Unit

  

  2014-03-26 - DMVs & CVs, General, Series, SQL Server Internals, Storage Wednesday

  SQL Server groups all pages that belong to a single partition of a single index or heap into logical units. These units are called allocation units. Read on to learn about the different types of allocation units and discover how to identify the allocation units belonging to a table.

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• The Extent (A Storage Wednesday Post)

  

  2014-03-19 - General, Series, SQL Server Internals, Storage Wednesday

  SQL Server organizes database pages in groups of 8 called extents. An extent is the smallest unit that SQL Server will reserve on disk. However, smaller tables are still possible through mixed extents. Read on to get all the details.

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• The Row Header (A Storage Wednesday Post)

  

  2014-03-12 - General, Series, SQL Server Internals, Storage Wednesday

  The row header contains metadata describing the row. It contains information about the row type, the column count and a NULL-bitmap. Read on to get all the details.

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