Possible Network File Damage with Redirector Caching

ID: 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.

The information in this article applies to:

Microsoft Windows 95

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, 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

To install this update, follow these steps:

Download the Vrdrupd.exe file from the online service listed below to an empty folder.

In My Computer or Windows Explorer, double-click the Vrdrupd.exe file you downloaded in step 1.

Follow the instructions on the screen.

The following file is available for download from the Microsoft Software Library. Click the file name below to download the file:

Vrdrupd.exe

Release Date: Mar-12-1996

For more information about how to download files from the Microsoft Software Library, please see the following article in the Microsoft Knowledge Base:

Q119591 How to Obtain Microsoft Support Files from Online Services

The following files are installed by Vrdrupd.exe:


   File name     Version    Date/Time        Size     Destination folder
   ---------------------------------------------------------------------
   Vredir.vxd    4.00.1116  6/2/97  11:16a   156,773  Windows\System
   Vnetsup.vxd   4.00.1112  5/30/97 11:12a    17,595  Windows\System

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\DiscardCacheOnOpen=1

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

Keywords : kbfile kbnetwork win95
Version : WINDOWS:95
Platform : WINDOWS
Issue type : kbprb