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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:
283037The 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.
(http://support.microsoft.com/kb/283037/ )Large memory support is available in Windows 2000 and Windows Server 2003
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:
Note You cannot allocate more than 4 GB of physical memory to an application on Windows 2000 Server because Physical Address Extension (PAE) is not available on Microsoft Windows 2000 Server. Also, you cannot use the 3 GB switch in the Boot.ini file with Windows 2000 Server; however, you can use the 3 GB switch in the Boot.ini file with Microsoft Windows 2000 Advanced Server or Microsoft Windows Datacenter versions. For more information, click the following article number to view the article in the Microsoft Knowledge Base:
(http://support.microsoft.com/kb/291988/ )A description of the 4 GB RAM Tuning feature and the Physical Address Extension parameter
Note The extended memory option in SQL Server 7.0 is not available on Windows 2000.
(http://support.microsoft.com/kb/268230/ )Scaling out versus scaling up with Intel Physical Addressing Extensions (PAE)
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.
Note The extended memory option in SQL Server 7.0 is not available on Windows 2000 Advanced Server or Windows Datacenter.
Microsoft Windows NT 4.0 Enterprise Edition
SQL Server 2000SQL Server 2000 Enterprise and Developer Edition requires the /3GB switch in the Boot.ini file in order to address up to 3 GB of available memory.
Note Windows NT 4.0 Enterprise Edition does not support the AWE memory architecture model so AWE support is not available.
SQL Server 7.0SQL 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.
For additional information, click the following article numbers to view the articles in the Microsoft Knowledge Base:
(http://support.microsoft.com/kb/170756/ )Available switch options for Windows NT Boot.ini file
(http://support.microsoft.com/kb/171793/ )Information on application use of 4GT RAM tuning
(http://support.microsoft.com/kb/268363/ )Intel Physical Addressing Extensions (PAE) in Windows 2000
(http://support.microsoft.com/kb/292934/ )Windows 2000 Datacenter Server does not locate memory greater than 16 GB
160606See the "Managing AWE Memory" topic and the "Running Multiple Instances and Using Failover Clustering" topic in SQL Server 2000 Books Online.
(http://support.microsoft.com/kb/160606/ )Performance enhancements for SQL Server under Windows NT
Article ID: 274750 - Last Review: December 23, 2005 - Revision: 7.3
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