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Extending Memory – AWE – exact limits.

Can someone please clarify the following as the online documentation is a little unclear. Question 1 relates to Windows 2000 Advanced Server, SQL Server 2000 Enterprise edition. 1) (RAM is 3.7GB) Documentation states when AWE is disabled maximum memory is 3GB. It also states when AWE is enabled you can use more than 4GB. When AWE is enabled can you use 3.5GB ? In other words more than the default 2GB, more than 3GB without the /3GB parameter (see below), and less than 4GB without the /PAE parameter. 2)Documentation states that when you use the /3GB parameter in the boot.ini file, this allows you to use 3GB of virtual memory, available memory, or address space. However documentation also states ‘user-mode memory’ is limited to 2GB when you use the /3GB paramter. What is the difference? Many Thanks.
By definition, a 32-bit processor uses 32 bits to refer to the location of each byte of memory. 2^32 = 4.2 billion, which means a memory address that’s 32 bits long can only refer to 4.2 billion unique locations (i.e. 4 GB). In the 32-bit Windows world, each application has its own “virtual” 4GB memory space. (This means that each application functions as if it has a flat 4GB of memory, and the system’s memory manager keeps track of memory mapping, which applications are using which memory, page file management, and so on.) This 4GB space is evenly divided into two parts, with 2GB dedicated for kernel usage, and 2GB left for application usage. Each application gets its own 2GB, but all applications have to share the same 2GB kernel space. KBAhttp://support.microsoft.com/default.aspx?scid=kb;en-us;274750 for reference. Satya SKJ
Microsoft SQL Server MVP
Contributing Editor & Forums Moderator
This posting is provided “AS IS” with no rights for the sake of knowledge sharing.
Hi Satya Thanks for the above. When you use the /3 GB parameter in the boot.ini file what is the user mode memory that is restricted to 2GB, if SQL Server gets 3GB??? Thanks