How to configure SQL Server to use more than 2 GB of physical memory (274750)

SUMMARY

This article describes how to configure SQL Server to use more than 2 GB of physical memory.

Microsoft SQL Server 7.0 and Microsoft SQL Server 2000 dynamically acquire and free memory as needed. When you run multiple instances of SQL Server on a computer, each instance dynamically acquires and frees memory to adjust for changes in the workload of the instance.

SQL Server 2000 Enterprise Edition introduces support for the use of Microsoft Windows 2000 Address Windowing Extensions (AWE) to address approximately 8 GB of memory for instances that run on Microsoft Windows 2000 Advanced Server, and approximately 32 GB for instances that run on Microsoft Windows 2000 Datacenter. With AWE, SQL Server can reserve memory that is not in use for other applications and the operating system. Each instance that uses this memory; however, must statically allocate the memory it needs. SQL Server can only use this AWE allocated memory for the data cache and not for executables, drivers, DLLs, and so forth. For additional information, click the following article number to view the article in the Microsoft Knowledge Base: The extended memory size option is available only for Microsoft SQL Server 7.0, Enterprise Edition on the operating system and hardware that supports the Enterprise Memory Architecture (EMA) feature. For more information about how to configure your system to enable the EMA feature on a particular system configuration, refer to your Microsoft Windows NT documentation.

Some system vendors may provide products for Microsoft Windows NT, version 4.0 or later, so that SQL Server 7.0, Enterprise Edition can use the extended memory size option. On Intel platforms, SQL Server 7.0 can use a feature known as PSE36. On Alpha platforms, the feature that allows use of the extended memory option is Very Large Memory (VLM). For more information about the availability, installation, and configuration of these products, contact your system vendor.

Note: To use Address Windowing Extensions (AWE) memory, you must run the SQL Server 2000 database engine under a Windows account that has been assigned the Windows lock pages in memory administrative credentials.

Note If you are using SQL Server 2005 to configure memory to use more than 2 GB of physical, see the following topics in SQL Server 2005 Books Online:

• Memory Architecture
• Server Memory Options
• Using AWE
• Enabling Memory Support for Over 4 Gb of Physical Memory
• Enabling AWE Memory for SQL Server

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Support for operating system versions

Windows 2000 Server

Windows 2000 Advanced Server or Windows 2000 Datacenter or Windows Server 2003

The maximum amount of physical memory addressable by a 32-bit addressing mode is 4 GB. All processors based on the IA-32 architecture that begin with the Intel Pentium Pro, support a new 36-bit physical addressing mode known as Physical Address Extension (PAE). PAE allows up to 8 GB of physical memory on Windows 2000 Advanced Server and up to 32 GB of physical memory on Windows 2000 Datacenter Server. This is because the tested memory limit on Windows 2000 Datacenter Server is 32 GB. The PAE mode kernel requires an Intel architecture processor, Pentium Pro, or later and either Windows 2000 Advanced Server or Windows 2000 Datacenter. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:

Note The maximum amount of memory that can be supported on Windows Server 2003 is 4 GB. However, Windows Server 2003 Enterprise Edition supports 32 GB of physical RAM. Windows Server 2003 Datacenter Edition supports 64 GB of physical RAM by using the Physical Address Extensions (PAE) feature. You can use the 3 GB switch that is in the Boot.ini file with Microsoft Windows Server 2003, Microsoft Windows Server 2003 Enterprise Edition, or with Microsoft Windows Server 2003 Datacenter Edition.

• Use of the /PAE switch in the Boot.ini and the AWE enable option in SQL Server allows SQL Server 2000 to utilize more than 4 GB memory. Without the /PAE switch SQL Server can only utilize up to 3 GB of memory.
  
  Note To allow AWE to use the memory range above 16 GB on Windows 2000 Data Center, make sure that the /3GB switch is not in the Boot.ini file. If the /3GB switch is in the Boot.ini file, Windows 2000 may not be able to address any memory above 16 GB correctly.
  
  When you allocate SQL Server AWE memory on a 32 GB system, Windows 2000 may require at least 1 GB memory to manage AWE.
  
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  Example

  The following example shows how to enable AWE and configure a limit of 6 GB for the max server memory option:

  sp_configure 'show advanced options', 1
  RECONFIGURE
  GO
  sp_configure 'awe enabled', 1
  RECONFIGURE
  GO
  sp_configure 'max server memory', 6144
  RECONFIGURE
  GO
  						

  
  
• -or-Use of the /3GB switch in the Boot.ini file allows SQL Server 2000 to use up to 3 GB of available memory.

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Microsoft Windows NT 4.0 Enterprise Edition

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SQL Server 7.0

SQL Server 7.0 Enterprise Edition requires the /3GB switch in the Boot.ini file in order to address up to 3 GB of available memory.


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