There is an inherent maximum of 4 GB of addressable memory for the 32 bit architecture. This is a maximum per process. one 4 GB memory segment is shared by all user threads. By default, if you run multiple Oracle instances on the same server, or run other applications on the same server, they will share the same 4 GB of memory.
By default, on Windows 2000 and Server 2003, 2 GB of the available 4 GB of memory is reserved for the 32-bit OS and 2 GB is shared for User Threads (i.e. the Oracle SGA). It is possible to allow Oracle to use more memory. To expand the total memory used by Oracle above 2 GB, the /3GB flag may be set in the boot.ini file. With the /3GB flag set, only 1 GB is used for the OS, and 3 GB is available for all user threads, including the Oracle SGA.
Workarounds are available for using memory above the 4 GB limit. Intel 32-bit processors such as the Xeon processor support Paging Address Extensions for large memory support. PAE allocates additional memory in a separate memory segment that is also assigned to the process. MS Windows 2000 and 2003 support PAE through Address Windowing Extensions (AWE). PAE/AWE may be enabled by setting the /PAE flag in the boot.ini file. The “USE_INDIRECT_BUFFERS=TRUE” parameter must also be set in the Oracle initialization file. In addition, the DB_BLOCK_BUFFERS parameter must be used instead of the DB_CACHE parameter in the Oracle initialization file.
With this method, Windows 2000 Server and Windows Server 2003 versions can support up to 8 GB of total memory.Windows Advanced Server and Data Center versions support up to 64 GB of addressable memory with PAE/AWE.
Recommanded changes for Windows x86 system Boot.ini SWITCH- < 4GB None (or /NOPAE)
- = 4GB /3GB (or /3GB /NOPAE)
- > 4GB to <= 16GB /3GB /PAE
- >16GB /PAE only
Support for /3GB and /PAE – 32-bit - Windows 2000 Advanced Server
- Windows 2000 Datacenter Server
- Windows 2003 Enterprise Edition
- Windows 2003 Datacenter Edition
32-bit Max Memory Support on x86 based computers
- Windows 2003 Enterprise = 32GB max
- Windows 2003 Datacenter = 64GB max
Some good links for oracle on windows
http://www.siebelonmicrosoft.com/technical_content/oracle/workshops.aspx
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