This article describes how to disable the Citrix SFO Alternate Stream driver (CtxAltStr.sys).

Background

CtxAltStr.Sys is the filter driver for memory optimization, a feature of Presentation Server that was first introduced in Presentation Server 4.0.
This driver intercepts all calls to the file system and checks to see if an Alternate Data Stream has been added to the file. If they have been added, it sends the alternate data stream back to the operating system.

This driver is always loaded into system memory when the server starts, even if the feature is disabled. This can be verified by using the Process Explorer, as shown in the following screen shot.

While troubleshooting server crash or memory leak issues, which could be attributed to CtxAltStr.Sys, you might be prompted to disable this driver and monitor the server to confirm the cause.

Instructions

Complete one of the following procedures to disable the CtxAltStr.Sys driver and test the server stability without uninstalling any of the product features:

• Editing the Registry

• Using the Device Manager

• Using the Autoruns tool of Microsoft

Editing the Registry

Caution! Refer to the Disclaimer at the end of this article before using Registry Editor.

To edit the Registry, complete the following procedure:

1. Open the following registry key:
   HKLM\SYSTEM\CurrentControlSet\Services\ctxaltstr

2. Change the DWORD value of Start to 0x4 (Disabled) instead of 0x2 (Automatic).

3. Restart the server.
   

Using Device Manager

1. Right click My Computer and select Properties to display the System Property page.
2. Activate the Hardware tab and click Device Manager.
3. Select View from the file menu and select Show hidden devices.
4. Expand Non-Plug and Play drivers and locate CtxAltStr.
5. Right click CtxAltStr and select Disable.
6. Restart the server.

Using the Autoruns tool of Microsoft

1. Start the AutoRuns tool.
   

2. Clear the option corresponding to the driver.

3. Restart the server.

Configure how a service is started