lotus domino: increase 2 gb physical memory limit (win 32-bit)


IBM Notes and Domino: Tips & Tricks

Lotus Domino: Increase 2 GB physical memory limit (Win 32-bit)
February 8, 2010

By Lance Zakin, PCLP
Enterprise Architect
Software Engineer
IBM BP NotesMail
This article will instruct you how to increase performance on your Domino Server by increasing the physical memory available to Domino from 2 GB to 3 GB. Windows 2003 Server (32-bit) and Windows 2000 Server (32-bit) can only support 4 GB maximum memory. Lotus Domino and other applications running on these operating systems can only utilize 2 GB physical memory plus virtual memory (hard drive swap file).

If your Windows Server has 4 GB memory installed you can configure it to allow Domino to use 3 GB physical memory as seen below. Windows can only allocate more than 2 GB physical memory to applications which are "Large Address Aware". Domino 7.0.1 and higher support "Large Address Aware".

4-Gigabyte Tuning (4GT)

On 32-bit editions of Windows, applications have 4 gigabyte (GB) of virtual address space available. The virtual address space is divided so that 2 GB is available to the application and the other 2 GB is available only to the system. The 4-gigabyte tuning (4GT) feature, formerly called 4GT RAM Tuning, increases the virtual address space that is available to the application up to 3 GB, and reduces the amount available to the system to between 1 and 2 GB.

For applications that are memory-intensive, such as database management systems (DBMS), the use of a larger virtual address space can provide considerable performance and scalability benefits. However, the file cache, paged pool, and nonpaged pool are smaller, which can adversely affect applications with heavy networking or I/O. Therefore, you might want to test your application under load, and examine the performance counters to determine whether your application benefits from the larger address space.

Windows Server 2003 and earlier: To enable 4GT, add the /3GB switch to the Boot.ini file. The /3GB switch is supported on the following systems:

* Windows Server 2003
* Windows XP Professional
* Windows 2000 Datacenter Server
* Windows 2000 Advanced Server

The /3GB switch makes a full 3 GB of virtual address space available to applications and reduces the amount available to the system to 1 GB.

Reference Sources

Lotus Domino support for the Windows /3GB switch:
http://www-01.ibm.com/support/docview.wss?uid=swg21257005

Memory Limits for Windows Releases:
http://msdn.microsoft.com/en-us/library/aa366778(VS.85).aspx

4-Gigabyte Tuning:
http://msdn.microsoft.com/en-us/library/bb613473%28VS.85%29.aspx

LOADED_IMAGE Structure:
http://msdn.microsoft.com/en-us/library/ms680349(VS.85).aspx

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