Microsoft KB Archive/148367

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Possible Network File Damage with Redirector Caching

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Q148367

IMPORTANT: This article contains information about editing the registry. Before you edit the registry, make sure you understand how to restore it if a problem occurs. For information about how to do this, view the "Restoring the Registry" Help topic in Regedit.exe or the "Restoring a Registry Key" Help topic in Regedt32.exe.

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The information in this article applies to:


 * Microsoft Windows 95

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SYMPTOMS
When you use the Microsoft Client for Microsoft Networks, a file on a Microsoft networking server (such as a Microsoft Windows NT, Windows 95, Microsoft Windows for Workgroups, or Microsoft LAN Manager server) may become damaged or may contain invalid data if multiple workstations access the file at the same time.

CAUSE
The network redirector (Vredir.vxd) caches data locally for files it accesses on a Microsoft networking server. If the file size does not change or if the last modified time does not change within a two-second period, the redirector reads file data from the locally stored cache rather than from the file on the server.

RESOLUTION
WARNING: Using Registry Editor incorrectly can cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that problems resulting from the incorrect use of Registry Editor can be solved. Use Registry Editor at your own risk.

For information about how to edit the registry, view the "Changing Keys and Values" Help topic in Registry Editor (Regedit.exe) or the "Add and Delete Information in the Registry" and "Edit Registry Data" Help topics in Regedt32.exe. Note that you should back up the registry before you edit it. If you are running Windows NT or Windows 2000, you should also update your Emergency Repair Disk (ERD).

This issue is resolved by the following updated file for Windows 95:

  VREDIR.VXD version 4.00.1112 (dated 2/11/97) and later The following file is available for download from the Microsoft Download Center:

"Download.gifoad Vredrupd.exe now]" For additional information about how to download Microsoft Support files, click the article number below to view the article in the Microsoft Knowledge Base:

"Q119591 How to Obtain Microsoft Support Files from Online Services" Microsoft used the most current virus detection software available on the date of posting to scan this file for viruses. Once posted, the file is housed on secure servers that prevent any unauthorized changes to the file.

This update resolves this issue by disabling caching on all FileOpen calls only if the following binary value is present in the registry:

HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\VxD\VREDIR

Value Name: DiscardCacheOnOpen

Value: 01 00 00 00 If this value is not present or is set to 0, this update behaves the same as Vredir.vxd versions 4.00.955 and earlier.

This value is not added by default and must be added manually in order to disable caching when opening files.

STATUS
This issue is resolved in Microsoft Windows 98.

MORE INFORMATION
For additional information about issues resolved by updates to this component, please see the following articles in the Microsoft Knowledge Base:

"Q172594 Cannot Connect to Server with 15 Characters and Period in Name" "Q165402 Windows 95 Update to Encrypt Passwords in Memory" "Q161100 File May Be Truncated When Copied to a Full Network Drive" "Q157114 'Access Denied' Attempting to Run File on LM/X Server" "Q156497 Duplicate Print Output on PC-LAN Server from Windows 95 Client" "Q152186 Possible Network Data Corruption If Locking Not Used" "Q142803 Hang or Locking Error Accessing Database Files Over Network" "Q140558 Deleting Files on Samba Servers May Delete Local Files Instead" "Q138249 Updated Vredir.vxd Corrects Errors Running Files on LMX" "Q160807 Cannot Connect to Windows NT Server with Many Shares" "Q150215 Disabling Automatic Network Shortcut Resolution" "Q138014 File May Be Truncated to Zero Bytes When Copied Onto Itself" "Q136834 Error Copying Read-Only Files to Core SMB Server" Additional query words: corrupt w95cn

Keywords : kbfile kbnetwork win95 kbgraphxlinkcritical

Issue type : kbprb

Technology : kbWin95search kbWin95