Using AWE memory in SQL Server 2000

Using AWE memory in SQL Server 2000
By: Brad mcgehee
May 31,200 3

If you are using SQL Server 2000 Standard Edition under Windows NT 4.0 or Windows 2000 (any version), or are running SQL Server 2000 Enterprise Edition under Windows NT 4.0 or Windows 2000 server, or if your server has 4 GB or less of RAM, the "awe enabled" option shoshould always be left to the default value of 0, which means that awe memory is not being used.

The awe (advanced drawing wing extensions) API allows applications (that are written to use the awe API) to run under Windows 2000 Advanced Server or Windows 2000 datacenter server to access more than 4 GB of RAM. SQL Server 2000 Enterprise Edition (not SQL Server 2000 Standard Edition) is awe-enabled and can take advantage of RAM in a server over 4 GB. if the operating system is Windows 2000 Advanced Server, SQL Server 2000 Enterprise Edition can us up to 8 GB of RAM. if the operating system is Windows 2000 datacenter server, SQL Server 2000 enterprise can use up to 64 GB of RAM.

By default, if a physical server has more than 4 GB of RAM, Windows 2000 (Advanced and datacenter), along with SQL Server 2000 Enterprise Edition, cannot access any Ram greater than 4 GB. in order for the operating system and SQL Server 2000 Enterprise Edition to take advantage of the Additional RAM, two steps must be completed.

Exactly how you configure awe memory support depends on how much ram your server has. to configure Windows 2000 (advanced or datacenter), you must enter one of the following switches in the boot line of the boot. INI file, and reboot the server:

• 4 gb ram:/3 GB (AWE support is not used)

• 8 gb ram:/3 GB/PAE

• 16 gb ram:/3 GB/PAE

• 16 GB + RAM:/PAE
The/3 GB switch is used to tell SQL Server to take advantage of 3 GB out of the base 4 GB of ram that Windows 2000 supports natively. if you don't specify this option, then SQL server will only take advantage of 2 GB of the first 4 GB of RAM in the server, essential tially wasting 1 GB of RAM.

awe memory technology is used only for the ram that exceeds the Base 4 GB of RAM, that's why the/3 GB switch is needed to use as much of the ram in your server as possible. if your server has 16 GB or less of RAM, then using the/3 GB switch is important. but if your server has more than 16 GB of RAM, then you must not use the/3 GB switch. the reason for this is because the 1 GB of Additional RAM provided by adding the/3 GB switch is needed by the operating system in order to take advantage of all of the extra awe memory. in other words, the operating system needs 2 GB of Ram itself to mange the awe memory if your server has more than 16 GB of RAM. if 16 GB or less of Ram is in a server, then the operating system only needs 1 GB of RAM, allowing the other 1 GB of RAM for use by SQL Server.

Once this step is done, the next step is to set the "awe enabled" option to 1 within SQL Server Enterprise Edition, and then restart the SQL Server service. only at this point will SQL Server be able to use the Additional RAM in the server.

One caution about using the "awe enabled" setting is that after turning it on, SQL Server no longer dynamically manages memory. instead, it takes all of the available RAM (Bytes t about 128 MB which is left for the operating system ). if you want to prevent SQL Server from taking all of the Ram, you must set the "Max Server Memory" option (described in more detail later in this article) to a figure that limits SQL Server to the amount or ram you specify. (7.0, 2000) Updated 1-2-2004