/3G question

We have some boxes with Sql 2000 sp4 on windows 2003 enterprise edition. 8G
total physical memory, boot.ini options with /PAE but without /3G. SQL AWE
enabled, and max server memeory configured to be 7G. From Task manager,
memory utilization is 7.2G. From perf mon, sql target mem is 7G and total
server memory both show 7G.
My question is, without /3G, how could SQL use more than 6G of memory? Am I
missing something here? and most importantly, is there any performance
implications configuring SQL to use 7G without /3G boot option?
Thanks very much.
Brian
AWE enables SQL Server (or any properly enabled app) to see up to 64GB of
memory with the proper OS and SQL Editions. The /3GB has nothing to do with
AWE (other than you should turn it off at 12GB or higher to ensure enough
PTEs). It only allows the app to see 3GB instead of 2GB of directly
addressable memory.
http://sqljunkies.com/Tutorial/0D4FF40A-695C-4327-A41B-F9F2FE2D58F6.scuk
Memory
http://www.sql-server-performance.com/awe_memory.asp Using AWE Memory
http://www.support.microsoft.com/?id=321363 SQL Server 7 & 2000 memory
usage
http://www.support.microsoft.com/?id=274750 Memory config
http://www.support.microsoft.com/?id=283037 Large Memory Support Is
Available in Windows 2000 (AWE)
http://www.support.microsoft.com/?id=811891 Can not use more than 2GB of
memory
Andrew J. Kelly SQL MVP
"Brian Brian" <BrianBrian@.discussions.microsoft.com> wrote in message
news:2DB937E4-6853-4EFB-B1F3-C23012F70734@.microsoft.com...
> We have some boxes with Sql 2000 sp4 on windows 2003 enterprise edition.
> 8G
> total physical memory, boot.ini options with /PAE but without /3G. SQL AWE
> enabled, and max server memeory configured to be 7G. From Task manager,
> memory utilization is 7.2G. From perf mon, sql target mem is 7G and total
> server memory both show 7G.
> My question is, without /3G, how could SQL use more than 6G of memory? Am
> I
> missing something here? and most importantly, is there any performance
> implications configuring SQL to use 7G without /3G boot option?
> Thanks very much.
> --
> Brian
|||Hi Brian
I'm not sure where you get the 6GB figure from. Without AWE, SQL Server is
limited to either 2GB or 3GB. With AWE, SQL Server can use up to 64GB,
depending on the version and edition. The /3GB switch only controls how
much memory is directly addressable. All memory above 2GB or 3GB must be
accessed through AWE memory mapping.
Direct addressing is slightly faster than going through AWE, so with the 3GB
flag you will get to more memory slightly faster. In addition, only pages
from your data files can use the memory addressed through AWE. All other
memory uses (query plan, user connections, lock memory, etc) has to use
directly addressed memory, so having 3GB enabled will give you up to 50%
more space for those other memory uses. This can be a good thing.
HTH
Kalen Delaney, SQL Server MVP
www.InsideSQLServer.com
http://sqlblog.com
"Brian Brian" <BrianBrian@.discussions.microsoft.com> wrote in message
news:2DB937E4-6853-4EFB-B1F3-C23012F70734@.microsoft.com...
> We have some boxes with Sql 2000 sp4 on windows 2003 enterprise edition.
> 8G
> total physical memory, boot.ini options with /PAE but without /3G. SQL AWE
> enabled, and max server memeory configured to be 7G. From Task manager,
> memory utilization is 7.2G. From perf mon, sql target mem is 7G and total
> server memory both show 7G.
> My question is, without /3G, how could SQL use more than 6G of memory? Am
> I
> missing something here? and most importantly, is there any performance
> implications configuring SQL to use 7G without /3G boot option?
> Thanks very much.
> --
> Brian