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Error message when you use a Windows Vista-based computer to try to access files on a Windows Vista-based file server: "<DriveLetter>:\ is not accessible. Insufficient system resources exist to complete the API"
Article ID: 938475 - 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
When you use a Windows Vista-based computer to try to access files on a Windows Vista-based file server, you may receive an error message that resembles the following:
DriveLetter:\ is not accessible.
Insufficient system resources exist to complete the API.
This problem occurs if you try to access the file by using a long-term Server Message Block (SMB) request, and if more than 64 concurrent long-term SMB requests are sent to the file server. In this situation, all other long-term SMB requests are not answered.
Note Unlike typical SMB requests, a long-term SMB request remains open until it is answered by the server. For example, a long-term request is sent when a client computer uses the FindFirstChangeNotification function to monitor a shared resource for changes.
In Windows Vista, the Server service intentionally limits the maximum number of concurrent asynchronous network requests to 64. A Windows Vista-based client computer also has this limitation. However, the file server processes typical SMB requests immediately.
Note If both of the file server and the client computer are Windows Vista-based computers, the SMB 2.0 protocol is used for file sharing operations.
To resolve this problem, apply the following hotfix to both the file server and the client computer. After you apply the hotfix, you must modify a registry entry on the server to configure the maximum number of concurrent SMB requests. For more information about how to do this, see the "Registry information" section.
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 informationA 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:
http://support.microsoft.com/contactus/?ws=supportNote The "Hotfix download available" form displays the languages for which the hotfix is available. If you do not see your language, it is because a hotfix is not available for that language.
PrerequisitesNo prerequisites are required.
Restart requirementYou have to restart your computer after you apply this hotfix.
Hotfix replacement informationThis hotfix does not replace any other previously released 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 resolve this problem, modify the AsynchronousCredits registry entry on the file server to configure the maximum number of concurrent SMB requests. To do this, 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.
SMB 2.0 is a new version of SMB that is designed for the latest networking environments and for the needs of the next generation of file servers. SMB 2.0 is the default protocol for Windows Vista-based file servers and for file servers that run Windows Server 2008.
For more information about SMB 2.0, visit the following Microsoft Web site:
http://technet.microsoft.com/en-us/library/bb726965.aspxFor more information about the FindFirstChangeNotification function, visit the following Microsoft Web site:
http://msdn2.microsoft.com/en-us/library/aa914108.aspxFor more information, click the following article numbers to view the articles in the Microsoft Knowledge Base:
(http://support.microsoft.com/kb/937082/ )You cannot configure the maximum number of concurrent SMB requests that are sent to a Windows Vista-based file server
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 configure the maximum number of concurrent SMB requests that are sent to the Server service in Windows XP
(http://support.microsoft.com/kb/824684/ )Description of the standard terminology that is used to describe Microsoft software updates
Article ID: 938475 - Last Review: October 8, 2011 - Revision: 4.0