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Article ID: 811169 - Last Review: January 12, 2015 - Revision: 6.0

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This article has been archived. It is offered "as is" and will no longer be updated.

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When you access files over a network, you may sometimes notice a small delay.


This problem occurs because the current redirector code in Windows XP performs certain operations that may affect performance when you access files over a network.

The Windows XP redirector currently performs the following behaviors that can affect performance:
  • The redirector does not cache directory contents for a long time.

    This may affect performance where there are a lot of FindFirst("*") calls.
  • The redirector disables collapsing on the file handles of files that have been extended so that directory information can be updated on the server more quickly.

    This may affect performance when a file is being opened after having been extended.
  • The redirector tries to close delayed closes when Read-Attribute-Only open operations occur for that file.

    This is to prevent a sharing violation from occurring on the server. This may affect performance because it is an unnecessary operation. A sharing violation does not occur for Read-Attribute-Only open operations.


Service pack information

To resolve this problem, obtain the latest service pack for Windows XP. For more information, click the following article number to view the article in the Microsoft Knowledge Base:
322389  ( ) How to obtain the latest Windows XP service pack

Hotfix information

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: (
Note 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.

File information

The 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 tool in Control Panel.
   Date         Time   Version             Size  File name   Platform 
   03-Dec-2002  19:34  5.1.2600.1147    399,488  Mrxsmb.sys  
   03-Dec-2002  19:34  5.1.2600.1147    154,752  Rdbss.sys   
   03-Dec-2002  19:35  5.1.2600.1147  1,256,192  Mrxsmb.sys  IA-64
   03-Dec-2002  19:35  5.1.2600.1147    488,704  Rdbss.sys   IA-64
This update performs the following:
  • It adds an opportunistic directory cache to the Server Message Block (SMB) mini-redirector.

    This improves performance by trying to cache the contents of a folder when a FindFirst("*") call occurs, and the network share where the folder resides has the unique name bit exposed.

    Note You can override this new setting by setting the DisableDirectoryCaching registry value to a non-zero value. To find the DisableDirectoryCaching registry entry, locate and then click the following registry subkey:
  • The redirector now sets a bit on the Fobx (the user handle) that indicates it has extended the file when it performs a write operation that extends the file.

    When that Fobx is closed, the redirector tries to send a Set-End-of-File command to the server to alert it to update directory information.
  • The redirector no longer follows the code path to close a delayed close when a Read-Attribute-Only open operation occurs.


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 Microsoft Windows XP Service Pack 2.

More information

After you install this update, performance benchmarking utilities such as Netbench may show a throughput increase of up to 21 percent.

Applies to
  • Microsoft Windows XP Professional x64 Edition
  • Microsoft Windows XP Home Edition
  • Microsoft Windows XP Professional
kbnosurvey kbarchive kbautohotfix kbhotfixserver kbqfe kbwinxpsp2fix kbwinxppresp2fix kbfix kbbug KB811169
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