3GB Switch on Windows 2003 R2 standard x-64

Posted on 2010-01-03
Last Modified: 2012-05-08
I read alot about the effect of the 3GB switch on windows server 2003 when we have 4 GB installed and we need to assign more memory to applications rather then the OS.
What i am asking for i need this in Windows 2003 R2 standard x64 ??
iIhave a server running with this OS with 8 GB RAM installed so how this memory is devided between the OS and the Applications?
Question by:mostabdo
    LVL 6

    Assisted Solution

    It is recommended to use 3GB switch if you have 32bit OS - that way one application can use more than 2GB ram.
    64-bit versions of Windows do not support the use of the /3GB switch in the boot options
    LVL 10

    Accepted Solution

    The 3GB switch isn't about RAM usage at all. It changes the normal 2GB application - 2GB system VIRTUAL address space division to 3GB application - 1GB system. In general it is NOT recommended that this setting be used unless you have applications that either need or would significantly benefit from the larger virtual address space. Most will not. There are some serious issues with this switch. But I don't think that is relevant to your situation.

    64 bit systems do not need or support this switch. In these systems the virtual address space is divided as 8TB private address space per application (for 64 bit native applications) and 8TB for the system. Again, this is VIRTUAL address space and has nothing to do with the size of RAM or how it is allocated This division is fixed and cannot be changed.

    32 bit applications running on a 64 bit OS will have a 2GB private virtual address space unless they indicate that they are large address space aware in which case this will be 4GB.

    RAM allocation between applications and the system is, and always has been, dynamic. There is no fixed division. The system dynamically assigns RAM according to need and availability. This applies to system components as well as applications.

    This series of articles describes the situation with 32 bit windows:
    This blog is by Raymond Chen, a senior developer with Microsoft.
    Read all of the articles carefully.


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