[windows_errors] [What_Error_Messages_Really_Mean_WinNT] Windows File System Tunneling Capabilities:
- From: "albertj809" <albertj809@xxxxxxxxx>
- To: What_Error_Messages_Really_Mean_WinNT@xxxxxxxxxxxxxxx
- Date: Sat, 13 Dec 2003 18:11:35 -0000
Windows NT Contains File System Tunneling Capabilities:
The information in this Article is for,
Windows NT Workstation 4.0 .
The Summary:
IMPORTANT: This article contains information about modifying the
registry.
Before you modify the registry, make sure to back it up and make
sure that you understand how to restore the registry if a problem
occurs.
For information about how to back up, restore, and edit the
registry, click the following Link to view the article.
Description of the Microsoft Windows Registry:
http://support.microsoft.com/default.aspx?scid=kb;EN-US;256986
The Windows products listed at the beginning of this article,
contain file system tunneling capabilities.
To enable compatibility with programs that rely on file systems
being able to hold onto file meta-info for a short period of time.
This occurs after deletion or renaming and re-introducing a new
directory entry with that meta-info, [if a create or rename occurs
to cause a file of that name to appear again in a short period of
time].
When a name is removed from a directory [rename or delete], it's
short/long name pair and creation time are saved in a cache, keyed
by the name that was removed.
When a name is added to a directory [rename or create], the cache is
searched to see if there is information to restore.
The cache is effective per instance of a directory. If a directory
is deleted, the cache for it is removed.
These paired operations can cause tunneling on "name."
delete(name)/create(name)
delete(name)/rename(source, name)
rename(name, newname)/create(name)
rename(name, newname)/rename(source, name)
The idea is to mimic the behavior MS-DOS programs expect when they
use the safe save method.
They copy the modified data to a temporary file, delete the original
and rename the temporary to the original.
This should seem to be the original file when complete.
Windows performs tunneling on both FAT and NTFS file systems to
ensure long/short file names are retained when 16-bit applications
perform this safe save operation.
How to See the Effects of Tunneling:
Create a file called file1.
Wait for one to two minutes.
Create a file called file2.
Perform a DIR /TC. Please note the creation times.
Rename file1 to file.
Rename file2 to file1.
Perform a DIR /TC.
Please note the creation times are identical.
Both files now show the same creation times; they are identical to
the original FILE1 creation time and is expected behavior with
tunneling enabled.
Here's some more information:
Tunneling cache time can be adjusted from the default time of 15
seconds, or if tunneling capabilities are undesirable, it can be
disabled by adding a value in the Windows Registry.
If tunneling is disabled, applications that use this safe save
method can lose the name they are unaware of, usually the LFN, and
the rediscovery of shortcut targets could be impaired since the
creation timestamps cannot remain constant for files manipulated by
such apps.
Creation timestamp maintenance is possible in the absence of
tunneling if an application is smart enough. The same is not true
for the long filenames.
...................................................................
WARNING: If you use Registry Editor incorrectly, you may cause
serious problems that may require you to reinstall your operating
system.
...................................................................
How to Increase Tunneling Cache Time:
Follow these steps, and then quit the Registry Editor.
Click Start, click Run, type regedit, and then click OK.
Locate and then click the following key in the registry:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\FileSystem
On the Edit menu, point to New, and then click DWORD Value.
Type MaximumTunnelEntryAgeInSeconds, and then press ENTER.
On the Edit menu, click Modify.
Type 30, and then click OK.
How to Disable Tunneling:
Follow these steps, and then quit the Registry Editor.
Click Start, click Run, type regedit, and then click OK.
Locate and then click the following key in the registry:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\FileSystem
On the Edit menu, point to New, and then click DWORD Value.
Type MaximumTunnelEntries, and then press ENTER.
On the Edit menu, click Modify.
Type 0, and then click OK.
....................................................................
Last Reviewed: 6/4/2003 (4.0)
====================================================================
Albert 172190
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