Tag: IAM page

• Page Type 3 – LOB Data Pages explained

  

  2014-07-23 - General, Series, SQL Server Internals, Storage Wednesday

  LOB data values in SQL Server are stored in separate allocation units in pages of type TEXT_MIX_PAGE. Read on and discover when these pages are used and how you can find out if your tables contain any pages of that type.

  [more…]

• The sys.dm_db_database_page_allocations DMF

  

  2014-07-09 - General, Series, SQL Server 2012, SQL Server Internals, Storage Wednesday

  Are you looking for an alternative to DBCC IND? Read on to see how the new sys.dm_db_database_page_allocations DMF can be used to return all pages for a particular table (or even all tables in a database).

  [more…]

• 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.

  [more…]

• 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.

  [more…]

• 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.

  [more…]