Article ID: 937082 - View products that this article applies to.
Important This article contains information about how to modify the registry. Make sure that you back up the registry before you modify it. Make sure that you know how to restore the registry if a problem occurs. For more information about how to back up, restore, and modify the registry, click the following article number to view the article in the Microsoft Knowledge Base:
(http://support.microsoft.com/kb/256986/ )Description of the Microsoft Windows registry
You cannot configure the maximum number of concurrent SMB requests that are sent to a Windows Vista-based file server.
When a Windows Vista-based computer is used as a file server, users access files by using long-term Server Message Block (SMB) requests. By default, only 10 SMB requests can be sent to the server at the same time. All other SMB requests are not answered. Therefore, the user of a client computer may receive an error message when the user tries to access files by using long-term SMB requests.
Note Unlike typical SMB requests, a long-term SMB request remains open until it is answered by the server. A typical long-term SMB request is the NotifyChange SMB request (NT_TRANSACT_NOTIFY_CHANGE).
This problem occurs because the Server service in Windows Vista is intentionally limited. By default, a restriction prohibits more than 10 concurrent SMB requests to be sent to the Server service in Windows Vista. Because Windows Vista is designed as a client operating system, Windows Vista is not optimized for server tasks.
Most SMB requests are processed immediately. However, long-term SMB requests may cause a problem.
Service pack informationTo resolve this problem, obtain the latest service pack for Windows Vista. For more information, click the following article number to view the article in the Microsoft Knowledge Base:
(http://support.microsoft.com/kb/935791/ )How to obtain the latest Windows Vista service pack
Hotfix informationTo resolve this problem, apply the following hotfix. This hotfix lets you use the MaxMpxCt registry entry to configure the maximum number of concurrent SMB requests. You can set the value of MaxMpxCt to a maximum of 255.
A supported hotfix is available from Microsoft. However, this hotfix is intended to correct only the problem that is described in this article. Apply this hotfix only to systems that are experiencing this specific problem. This hotfix might receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next software update that contains this hotfix.
If the hotfix is available for download, there is a "Hotfix download available" section at the top of this Knowledge Base article. If this section does not appear, contact Microsoft Customer Service and Support to obtain the hotfix.
Note If additional issues occur or if any troubleshooting is required, you might have to create a separate service request. The usual support costs will apply to additional support questions and issues that do not qualify for this specific hotfix. For a complete list of Microsoft Customer Service and Support telephone numbers or to create a separate service request, visit the following Microsoft Web site:
PrerequisitesNo prerequisites are required.
Restart requirementYou must restart the computer after you apply this hotfix.
Hotfix replacement informationThis hotfix does not replace any other hotfixes.
Registry informationWarning Serious problems might occur if you modify the registry incorrectly by using Registry Editor or by using another method. These problems might require that you reinstall the operating system. Microsoft cannot guarantee that these problems can be solved. Modify the registry at your own risk.
To enable this hotfix, follow these steps:
File informationThe English version of this hotfix has the file attributes (or later file attributes) that are listed in the following table. The dates and times for these files are listed in Coordinated Universal Time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time item in Control Panel.
Windows Vista, 32-bit versions
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Windows Vista, 64-bit versions
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Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section. This problem was first corrected in Windows Vista Service Pack 1.
The maximum value of concurrent SMB requests is equal to the minimum of the following two values:
On a Windows Vista-based server, the MaxMpxCt entry, the MaxWorkItems entry, and the Size entry are located in the following registry subkey:
On a Windows Vista-based client computer, the MaxCmds entry is located in the following registry subkey:
You must set the following registry entries on the server.
For more information about this problem in Microsoft Windows XP, click the following article number to view the article in the Microsoft Knowledge Base:
926646For more information about the terms that are used to describe software updates, click the following article number to view the article in the Microsoft Knowledge Base:
(http://support.microsoft.com/kb/926646/ )You cannot increase the limit concurrent SMB command in the Windows XP Professional Server service
(http://support.microsoft.com/kb/824684/ )Description of the standard terminology that is used to describe Microsoft software updates
Article ID: 937082 - Last Review: October 8, 2011 - Revision: 4.0