Tag: GAM

• Differential Changed Map (DCM): How SQL Server Tracks Changed Pages

  

  2014-05-07 - Backup, General, Series, SQL Server Internals, Storage Wednesday

  SQL Server uses the Differential Changed Map to determine, which pages changed since the last full backup. Read on to find out how the DCM is working.

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• PFS Pages: How SQL Server tracks “Page Free Space”

  

  2014-04-30 - General, Series, SQL Server Internals, Storage Wednesday

  PFS pages contain information about the free space available on all pages in a database file. They contain one byte per page that also holds four additional status bits. Read on to discover how to interpret the PFS data.

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• The Shared Global Allocation Map (SGAM)

  

  2014-04-23 - General, Series, SQL Server Internals, Storage Wednesday

  Discover how SQL Server tracks mixed extents containing free pages using a Shared Global Allocation Map made up of one SGAM page per GAM Interval.

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• 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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