Things to consider before you enable System cache mode in Windows XP (895932)

INTRODUCTION

System cache mode controls the partitioning between the memory that Microsoft Windows allocates to file caching and the memory that Windows allocates to applications. System cache resources are partitioned during startup and do not change. System cache mode is designed to improve the performance of Windows servers by increasing the system's file cache size. Web servers and other server-based file sharing programs generally perform better when information is read from the system cache instead of read repeatedly from the hard disk. When the system cache is used appropriately, file server performance improves.

If performance improves by switching from System cache mode to Programs mode, the operating system is being presented with a low memory resource condition. This condition affects the whole system. Any driver that asks for more resources may not receive the requested resources. Each driver and application may handle this resource limitation differently. Therefore, the root cause is difficult to identify.

Note By default, System cache mode is enabled in Microsoft Windows Server 2003. By default, the mode is disabled in Microsoft Windows XP.

MORE INFORMATION

System cache mode is designed for use with Windows server products that act as servers. System cache mode is also designed for limited use with Windows XP, when you use Windows XP as a file server. This mode is not designed for everyday desktop use. If you use a server product as a desktop, you should consider changing the resource allocation to Programs mode or adding more physical RAM.

When you enable System cache mode on a computer that uses Unified Memory Architecture (UMA)-based video hardware or an Accelerated Graphics Port (AGP), you may experience a severe and random decrease in performance. For example, this decrease in performance can include very slow system performance, stop errors, an inability to start the computer, devices or applications that do not load, and system instability.

The drivers for these components consume a large part of the remaining application memory when they are initialized during startup. Also, in this scenario, the system may have insufficient RAM when the following conditions occur:

Other drivers and desktop user services request additional resources.
Desktop users transfer large files.

To configure the system cache in Windows XP, follow these steps:

Click Start, click Run, type sysdm.cpl, and then click OK.
Click the Advanced tab.
In the Performance area, click Settings.
Click the Advanced tab.
In the Memory usage area, choose one of the following configurations:
- Click Programs if you are using this computer as a workstation instead of as a server. Your programs will run faster, and your system cache will be the default size that came with Windows XP.
- Click System cache if you use this computer as a server or if you use programs that require a large system cache.
Click Apply, and then restart the computer.

System cache mode enables the LargeSystemCache registry entry that is located under the following registry subkey:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management

Note If the computer does not start, you can select the Last Known Good Configuration option when you start the computer. This will reset the LargeSystemCache registry entry setting back to its default setting.

For more information about the LargeSystemCache registry entry, visit the following Microsoft Web page:

http://technet2.microsoft.com/windowsserver/en/library/EFA621BD-A031-4461-9E72-59197A7507B61033.mspx

For more information about related topics, click the following article number to view the article in the Microsoft Knowledge Base:

189327 How to map adapter RAM into process address space