Logon delays over slow links if oplock is not granted for the policy file in Windows (319440)

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Clients are effected by this slow logon behavior when the policy file is being downloaded. Administrators can disable slow-link detection (by using Administrator Templates\System\Group Policy), to force policy downloads regardless of the link speed. Each modification of the policy file causes the Registry.pol file to be downloaded by remote clients, for every change. For more information about how a slow link is detected and the default behavior of Group Policy extensions over slow link, click the following article numbers to view the articles in the Microsoft Knowledge Base: By default, the redirector attempts to get an 'Opportunistic Lock' when a file is opened remotely. This enables the redirector to use read-ahead caching to improve performance. For more information about oplocks, click the following article number to view the article in the Microsoft Knowledge Base: In certain cases, the file server may reject oplock requests, and this often occurs if the file is locked for exclusive/write use. Additionally, the Server service performs several other checks to prevent data damage and improve stability:

• Check to determine if the file is a system file.
• Check to determine if the network link is considered reliable.
• Check to determine if there are filter drivers that haven't finished their job.

For more information about a related topic, click the following article number to view the article in the Microsoft Knowledge Base: The users that access the files by using oplocks do not experience this behavior because the redirector performs read-ahead caching, and file reads are served from the redirector cache.

If the redirector does not open the remote file by using opportunistic locking, the Windows NT 4.0 SMB or CIF 2.0 specification from MSDN states: This causes the policy load method reads to access the server by using the network for each Unicode character that is read. If the policy file is large, and if the available bandwidth to the clients is low, significant delays occur while policies are loading, and this create logon delays.

To identify this situation, use any of the following methods.

Method 1

You can run the third-party Filemon.exe tool from the following Sysinternals Web site: Microsoft provides third-party contact information to help you find technical support. This contact information may change without notice. Microsoft does not guarantee the accuracy of this third-party contact information.

The output from the Filemon.exe tool is similar to:

Method 2

Microsoft network monitor traces display Oplock Level=none for the server response to the file open request:
The sequential 2 byte reads to the policy file, making it a slow download if the file is large:

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