Q222604: Configuring Cached Dfs Referral Expiration Time in Dfs 4.1
Article: Q222604
Product(s): Microsoft Windows NT
Version(s): winnt:4.0 SP3,4.0 SP4
Operating System(s):
Keyword(s):
Last Modified: 11-JUN-2002
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The information in this article applies to:
- Microsoft Windows NT Server versions 4.0 SP3, 4.0 SP4
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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 article number to view the article in the Microsoft Knowledge Base:
Q256986 Description of the Microsoft Windows Registry
SYMPTOMS
========
If the target directory of a Dfs volume is modified, clients do not become aware
of the change for a whole week, unless they are restarted.
It takes a week because the Cached Dfs Referral Expiration time is one week. In
some versions of Dfs, this value is hard-coded.
CAUSE
=====
As documented in the release notes of Dfs 4.1, the "Cached Dfs referral
expiration has been extended from 5 minutes to 1 week, to improve response times
and reduce load on the root server." This value is hard-coded, and cannot be
modified by the user in the base release of Dfs 4.1.
In Dfs 4.0, the cached Dfs referral expiration time was hard-coded to five
minutes. This ensures that changes are communicated promptly to clients, but it
can generate significant amounts of Dfs-related network traffic.
In Dfs 4.1, the cached Dfs referral expiration time was changed to a hard-coded
value of one week. This minimizes the amount of Dfs-related network traffic, but
changes to Dfs referrals will not be communicated to clients for one week,
unless the Dfs clients are restarted.
In networks where Dfs references are changed on a regular basis, the new
expiration time of one week is too long for clients to efficiently reflect the
changes.
RESOLUTION
==========
A supported fix is now available from Microsoft, but it is only intended to
correct the problem described in this article and should be applied only to
systems experiencing this specific problem. This fix may receive additional
testing at a later time, to further ensure product quality. Therefore, if you
are not severely affected by this problem, Microsoft recommends that you wait
for the next Windows NT 4.0 service pack that contains this fix.
To resolve this problem immediately, contact Microsoft Product Support Services
to obtain the fix. For a complete list of Microsoft Product Support Services
phone numbers and information about support costs, please go to the following
address on the World Wide Web:
http://support.microsoft.com/default.aspx?scid=fh;EN-US;CNTACTMS
NOTE: In special cases, charges that are normally incurred for support calls may
be canceled, if a Microsoft Support Professional determines that a specific
update will resolve your problem. Normal support costs will apply to additional
support questions and issues that do not qualify for the specific update in
question.
The English-language version of this fix should have the following file
attributes or later:
Date Time Size File name Platform
-------------------------------------------------------------
98/10/28 21:33 62,096 Dfs.sys (x86)
98/10/28 21:34 106,576 Dfs.sys (Alpha)
WARNING: If you use Registry Editor incorrectly, you may cause serious problems
that may require you to reinstall your operating system. Microsoft cannot
guarantee that you can solve problems that result from using Registry Editor
incorrectly. Use Registry Editor at your own risk.
After applying the fix and before restarting the computer, add the following
value to the registry to specify the value for the cached Dfs referral
expiration time:
1. Start Registry Editor (Regedt32.exe).
2. Locate the following key in the registry:
HKEY_LOCAL_MACHINE\Software\Microsoft\DfsHost\volumes
NOTE: The above registry key is one path; it has been wrapped for readability.
3. On the Edit menu, click Add Value, and then add the following registry value:
Value Name: TimeToLiveInSecs
Data Type: REG_DWORD
Value: cached Dfs referral expiration time in seconds
Default: 604800 seconds (one week)
4. Quit Registry Editor.
WORKAROUND
==========
To work around this problem, restart the Dfs clients.
STATUS
======
Microsoft has confirmed this to be a problem in Windows NT 4.0.
MORE INFORMATION
================
You should choose a value for TimeToLiveInSecs that is appropriate for your
network.
If your Dfs configuration is stable, a large value is recommended to reduce the
amount of Dfs-related traffic to a minimum. In such static Dfs networks, the
default value of one week may be perfectly appropriate.
You should only need to consider configuring a smaller value if your Dfs
configuration is so volatile that the frequency of workstation restarts required
to access the correct locations through Dfs becomes disruptive to normal
production work.
The amount of Dfs-related network traffic is directly proportional to the number
of Dfs clients on your network -- doubling the number of clients will double the
traffic.
Furthermore, the amount of Dfs-related network traffic is inversely proportional
to the value chosen for TimeToLiveInSecs -- halving this value will double the
traffic.
These points should be considered carefully before you modify TimeToLiveInSecs.
It is also recommended that you monitor network traffic volumes after reducing
the value of TimeToLiveInSecs, using Network Monitor for example, to ensure that
the amount of Dfs-related traffic is not excessive, and is not impacting network
performance and throughput.
Additional query words: 4.00
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Keywords :
Technology : kbWinNTsearch kbWinNT400search kbWinNTSsearch kbWinNTS400sp4 kbWinNTS400sp3 kbWinNTS400search
Version : winnt:4.0 SP3,4.0 SP4
Hardware : ALPHA x86
Issue type : kbbug
Solution Type : kbfix
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