Using the /3gb switch

All of our CES Installations are done on Windows servers (32-bit). Windows Servers, by default do not allow any process to utilise more than 2GB of memory in the RAM. With the maximum addressable space being 4GB for 32-bit OS, 2 GB is utilised by the Windows Kernel processes. Extended memory of upto 16GB can be used on the server and the extended memory is detected only by the Enterprise edition of Windows Server.
Even though, upto 10GB of RAM is available to be utilised, default settings on windows do not allow the Oracle Database to acquire more than 2GB (irrespective of the Physical Address space defined). To allow the Oracle Database instance to acquire more than 3GB, we have to turn on the /3gb switch on the Operating System.

In Windows 2003 Server
In Windows 2003 Server (Enterprise Edition), the 3GB switch can be turned ON using the boot.ini file
Note: The boot.ini file is available in the default drive (C:). You might have to show hidden and system files to view and edit the file.
Open the boot.ini file and locate Operating System parameters.

1. At the end of the parameter list, Add /3gb
   

   
   multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft Windows XP Professional" /fastdetect /usepmtimer /NoExecute=OptOut /3gb
   

   
   


2. Save the boot.ini file


3. Restart the Server for the changes to take effect

For more about the /3gb switch on Windows 2003 Server, read this

On Windows 2008 Server
On the Windows 2008 Server (or Vista OS), the 3gb switch can be turned ON/OFF using the Boot Configuration Data Editor (BCDEdit). [Read more about BCD]
To turn ON the 3GB Switch,

1. Run the Command Prompt (cmd) as Administrator.


2. Type
   

   
   bcdedit /set IncreaseUserVA 3072
   

   
   and press Enter

3072 = 3 * 1024 MB = 3GB

3. Restart the Server


4. Type bcdedit on command prompt to check the current value of IncreaseUserVA

To Turn OFF the 3GB switch, type

bcdedit /deletevalue IncreaseUserVA