Copying Files with Mix of LFN and SFN May Lead to Data Loss

ID: Q195144

The information in this article applies to:
  • Microsoft Windows NT Workstation version 4.0
  • Microsoft Windows NT Server version 4.0
  • Microsoft Windows NT Server, Enterprise Edition version 4.0
  • Microsoft Windows 95

SYMPTOMS

When files are copied from a source having a mixture of short filenames and long filenames, the copy operation may lead to lost files.

This problem can happen when the copy operation is performed using any of the following programs:

  • COPY


  • XCOPY


  • Windows NT Explorer


  • Windows NT Backup



CAUSE

This problem happens when a file with a long filename is copied and a new short filename is generated for the file in the destination folder. If a file exists in the source folder and it has a name matching the newly generated short filename, this file will replace the first file and the content of the first file is lost. For example:


   Source Directory :

   C:\source> dir /x

   08/21/98  02:03p        <DIR>                          .
   08/21/98  02:03p        <DIR>                          ..
   08/20/98  02:32p                     17                YXXXXX~1.XXX
   08/20/98  02:32p                     7 YXXXXX~2.XXX    yxxxxxxxxx.xxx
     4 File(s)              14 bytes

   C:\source> copy *.* c:\dest
   yxxxxxxxxx.xxx
   YXXXXX~1.XXX
        2 file(s) copied.

   C:\source> dir c:\dest

   09/15/98  09:27a        <DIR>                          .
   09/15/98  09:27a        <DIR>                          ..
   08/20/98  02:32p                     17 YXXXXX~1.XXX   yxxxxxxxxx.xxx
     3 File(s)             17 bytes

NOTE: The File yxxxxxxxxx.xxx gets copied first and the short filename generated for that is YXXXXX~1.XXX. When the copy program copies YXXXXX~1.XXX to the destination, it finds a match in file name and replaces the existing file with its contents.

In NTBackup, if both the short named file, and the NTFS converted long file names are the same, you are prompted whether to replace the existing file or not. Overwriting the file may result in data loss as the file names will be the same but the contents will not be.


RESOLUTION

Windows NT 4.0 with Internet Explorer 4

To resolve this problem, obtain the latest service pack for Windows NT 4.0 or the individual software update. For information on obtaining the latest service pack, please go to:
For information on obtaining the individual software update, contact Microsoft Product Support Services. For a complete list of Microsoft Product Support Services phone numbers and information on support costs, please go to the following address on the World Wide Web:
http://www.microsoft.com/support/supportnet/overview/overview.asp

Windows NT 4.0 without Internet Explorer 4

To resolve this problem, obtain the latest service pack for Windows NT 4.0 or the individual software update. For information on obtaining the latest service pack, please go to:
For information on obtaining the individual software update, contact Microsoft Product Support Services. For a complete list of Microsoft Product Support Services phone numbers and information on support costs, please go to the following address on the World Wide Web:
http://www.microsoft.com/support/supportnet/overview/overview.asp

Windows 95 with Internet Explorer 4.0

A supported fix that corrects this problem is now available from Microsoft, but it has not been fully regression tested and should be applied only to systems experiencing this specific problem.

To resolve this problem, contact Microsoft Product Support Services to obtain the fix. For a complete list of Microsoft Product Support Services phone numbers and information on support costs, please go to the following address on the World Wide Web:
http://www.microsoft.com/support/supportnet/overview/overview.asp
The English version of this fix should have the following file attributes or later:

   Date      Time                 Size    File name     Platform
   -------------------------------------------------------------
   03/02/99  06:40p             1,431,264 Shell32.dll   (Windows 95)

NOTE: The fixes mentioned above only fixes Windows NT Explorer initiated copies. The COPY/XCOPY behaviour is unchanged by design.


WORKAROUND

You can work around this problem by using the Windows NT Resource Kit utility, Robocopy, to copy the files.

Windows NT Backup

If the short file named files (for example, Drawg~12.dwg) are created by legacy applications and these applications cannot be upgraded, the following methods can be employed:
  • Use the FAT formatted partitions on Windows NT Servers for compatibility with these applications and use share-level security.


The following are less optimum workarounds but are mentioned here for convenience.
  • Disable the auto-generation of the short file names on NTFS volumes as per the following article in the Microsoft Knowledge Base:

    Q210638 How to Disable Automatic Short File Name Generation


  • Use different directories for long and short named files.



STATUS

Microsoft has confirmed this to be a problem in the Microsoft products listed at the beginning of this article. This problem was first corrected in Windows NT 4.0 Service Pack 5.

Additional query words: 4.00

Keywords : kbbug4.00 kbfix4.00 nt4sp5fix
Version : WINDOWS:95; winnt:4.0
Platform : WINDOWS winnt
Issue type : kbbug


Last Reviewed: August 27, 1999
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