awe enabled Option

In Microsoft® SQL Server™ 2000, you can use the Microsoft Windows® 2000 Address Windowing Extensions (AWE) API to support up to a maximum of 64 gigabytes (GB) of physical memory. The specific amount of memory you can use depends on hardware configuration and operating system support.

Note  This feature is available only in the SQL Server 2000 Enterprise and Developer editions.

Enabling AWE

To enable AWE, set awe enabled to 1. SQL Server will reserve almost all available memory, leaving 128 megabytes (MB) or less, unless a value has been specified for max server memory.

If the option has been successfully enabled, the message "Address Windowing Extension enabled" is printed in the SQL Server error log when the instance of SQL Server 2000 is started.

awe enabled is an advanced option. If you are using the sp_configure system stored procedure to change the setting, you can change awe enabled only when show advanced options is set to 1. You must restart the instance of SQL Server 2000 for changes to take effect.

Disabling AWE

To disable AWE, set awe enabled to 0. This setting is the default. The AWE API is not used. SQL Server 2000 operates in a normal dynamic memory allocation mode and is limited to 3 GB of physical memory.

Usage Considerations

Before enabling AWE, consider the following:

• When awe enabled is set to 1, instances of SQL Server 2000 do not dynamically manage the size of the address space. SQL Server will reserve and lock almost all available memory (or the value of max server memory if the option has been set) when the server is started. It is strongly recommended that you set a value for the max server memory option each time you enable AWE. Otherwise other applications or instances of SQL Server 2000 will have less than 128 MB of physical memory in which to run.
  
  
• If the total available memory is less than 3 GB, the instance of SQL Server 2000 will be started in non-AWE mode even if awe enabled is set to 1. In this situation, you do not need to manage AWE memory because dynamic memory allocation is used automatically.
  
  
• You can determine the amount of memory you can safely allocate to instances of SQL Server 2000 by identifying how much memory is available after all other applications to be used on the computer have been started. 

  Use the SQL Server Performance Monitor Total Server Memory (KB) counter to determine how much memory is allocated by the instance of SQL Server running in AWE mode. Configure the max server memory option to leave some additional memory free to allow for the varying needs of other applications and Windows 2000. For more information, see Monitoring Memory Usage.

Important  Using the awe enabled option and the max server memory setting can have a performance impact on other applications or on SQL Server running in a multi-instance or cluster environment. For more information about using AWE memory, see Managing AWE Memory.

Example

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

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

See Also

Memory Architecture

SQL Server: Buffer Manager Object

RECONFIGURE

Setting Configuration Options

sp_configure