Category: SQL Server Internals

• Bulk Changed Map (BCM): The Minimally Logged Advantage

  

  2014-05-14 - General, Series, SQL Server Internals, Storage Wednesday

  The Bulk-Logged recovery mode can provide a performance gain for your database. Check out how SQL Server uses the Bulk Changed Map to make this possible.

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• 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 Global Allocation Map (GAM)

  

  2014-04-16 - General, Series, SQL Server Internals, Storage Wednesday

  SQL Server uses the Global Allocation Map (GAM) to catalog if an extent is allocated or not. In a 7988-byte bitmap each extent is associated with a single bit to convey that information. Read on to get all the details.

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