SQL 2005 memory and the AWE caveat (i think)

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SQL 2005 memory and the AWE caveat (i think)

Dean Jones-454305

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August 3, 2009 at 9:27 am

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Hi,
Just a quick question guys.
I was looking at all the edition comparison for SQL 2005, and it does say that SQL 2005 standard does use OS maximum for memory, but my questions are as follows:
If SQL 2005 uses all the memory available to the OS, so why do we still need to enable AWE for SQL to address more memory.
Also, if one looks at the SQL target server memory and total server memory, without AWE enabled the figure comes up to about 1.6GB. Is there a caveat here on this topic as I notice that once AWE is enabled, then the memory figure jumps up.
http://www.microsoft.com/sqlserver/2005/en/us/compare-features.aspx
Thanks.

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schep021 Hall of Fame Points: 3538 More actions · Answer 1

Dean Jones (8/3/2009)
Hi,
Just a quick question guys.
I was looking at all the edition comparison for SQL 2005, and it does say that SQL 2005 standard does use OS maximum for memory, but my questions are as follows:
If SQL 2005 uses all the memory available to the OS, so why do we still need to enable AWE for SQL to address more memory.
Also, if one looks at the SQL target server memory and total server memory, without AWE enabled the figure comes up to about 1.6GB. Is there a caveat here on this topic as I notice that once AWE is enabled, then the memory figure jumps up.
http://www.microsoft.com/sqlserver/2005/en/us/compare-features.aspx
Thanks.

I can see how this would confuse you.

The following should help explain why you only see 1.6GB before enabling AWE.

Standard 32-bit addresses can map a maximum of 4 GB of memory. The standard address spaces of 32-bit processes are therefore limited to 4 GB. By default, on 32-bit Microsoft Windows operating systems, 2 GB are reserved for the operating system, and 2 GB are made available to the application...

http://technet.microsoft.com/en-us/library/ms175581%28SQL.90%29.aspx

This site has good advice as well:

http://www.sql-server-performance.com/tips/awe_memory_p1.aspx

Dean Jones-454305 SSCarpal Tunnel Points: 4804 More actions · Answer 2

Thanks for the reply, I assume that its only SQL x86 that suffers from this limitation ?

sturner SSC-Insane Points: 22411 More actions · Answer 3

64 bit versions of Windows OS can handle 32GB

The probability of survival is inversely proportional to the angle of arrival.

Richard M. SSCertifiable Points: 7401 More actions · Answer 4

sturner (8/4/2009)
64 bit versions of Windows OS can handle 32GB

The amount of memory SQL can use depends on the OS in use.

See this chart for comparison.

And here you can see how SQL behaves depending on its version.

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