3GB Maximum free memory space in a Windows 32-bit system

Http://msdn.microsoft.com/zh-cn/library/ms189334.aspx Process Address space

All 32-bit applications have a 4 GB process address space (32-bit addresses can map up to 4 GB of memory). For the Microsoft Windows operating system, applications can access the 2 GB process address space, called the user mode virtual address space. All threads that an application owns share the same user-mode virtual address space. The remaining 2 GB is reserved for the operating system (also known as the kernel mode address space). All operating system versions (starting with Windows Server 2003) have an boot. INI switch that provides the application with access to the 3 GB process address space, limiting the kernel-mode address space to 1 GB.

The next version of Microsoft SQL Server will remove the feature. Do not use this feature in new development work, and modify applications that are currently using the feature as soon as possible.

Address Windowing Extensions (AWE) extend the functionality of 32-bit applications by allowing access to as many operating systems as possible to support physical memory. AWE enables this functionality by mapping a portion of the maximum memory capacity to a user address space. The mapping between the application buffer pool and the AWE mapped memory is done by manipulating the Windows virtual memory table.

To support 3 GB of user-mode process space, you must add the /3GB parameter to the boot. ini file and restart the computer for the /3GB parameter to take effect. When this parameter is set, the user application thread can address 3 GB of process addressing space while reserving 1 GB of process address space for the operating system.

Attention

If there is more than more than 2 GB of available physical memory on the computer, the operating system requires a process address space of 2 GB for the system to use, and therefore only supports a user-mode address space of more than one. In order for AWE to be able to use more than GB of memory, ensure that the boot. ini file does not have the /3GB parameter. Otherwise, the operating system will not be able to address more than GB of memory.

Please seeConceptual Memory Architecture using AWE

The maximum free memory space for a process in a Windows 32-bit system is 3GB (RPM)