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Q233082: Windows Terminal Server Clients May Randomly Hang for 35 Seconds

Article: Q233082
Product(s): Microsoft Windows NT
Version(s): winnt:4.0
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 version 4.0, Terminal Server Edition 
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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
========

Terminal Server clients may experience an intermittant loss of responsiveness or
the client may appear to stop responding (hang) while running programs on the
Terminal Server computer. This problem only occurs if one or more users try to
gain access to files on other file servers on the network. When the client
hangs, all user sessions connected to the Terminal Server computer are affected
and the lack of responsiveness may last for 35 seconds or more.

CAUSE
=====

This problem occurs because each Terminal Server client is typically allowed to
have one outstanding command, such as a file open or read request to each remote
server at a time. When a file operation, such as file open, is sent to a server
for a file that is currently in use, the server may send a break oplock request
to the client that has the file open. This allows the client owning the locked
file a chance to flush any buffered changes before shared use is allowed.

In the case where the client issues a new file open request for a file it already
has open, the redirector may temporarily deadlock when the break oplock is
received from the server. After sending the oplock break request, the server
gives the client 35 seconds, which is the default setting to respond. When the
timeout occurs, the server responds to the new file request, breaking the
deadlock.

RESOLUTION
==========

To resolve this problem, install Windows NT Server 4.0, Terminal Server Edition
Service Pack 4 (SP4). Service Pack 4 provides an option that forces each client
to negotiate a session with all remote servers to which it is connected. The
negotiation allows the server to specify the number of commands the client may
have outstanding at a time, which by default, is 50.

MORE INFORMATION
================

On the Terminal Server computer, disabling the redirector parameter
MultipleUsersOnConnection increases the number of outstanding commands from 1 to
whatever number the server is able to support. Disabling this option also
corrects problems in installations where Terminal Server clients run programs
that open a large number of files or gain access to shared files, such as
databases. The impact of this option is that additional memory is used by the
redirector on the Terminal Server computer and on any servers to which the
client is connected. The amount of memory used varies based on configuration and
usage. Additionally, when a client first connects to a remote server, the client
sends one or more negotiate commands and then connects to the resource. If the
option is left at the default setting, only the first client connecting to a
remote server goes through the negotiate process, all other clients immediately
attempt to connect to the resource.

For additional information, click the article numbers below to view the articles
in the Microsoft Knowledge Base:

  Q152734 How to Obtain the Latest Windows NT 4.0 Service Pack
  Q190162 Terminal Server and the 2048 Open File Limitation
  Q231798 Access Database with Multiple Users Slow on Terminal Server

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.

To enable the new functionality, perform following steps:

1. Ensure that the server is running SP4 or later.

2. Start Registry Editor (Regedt32.exe).

3. Locate the following key in the registry:

  HKEY_LOCAL_MACHINE\\SYSTEM\CurrentControlSet\Services\Rdr\Parameters

4. On the Edit menu, click Add Value, and then add the following registry value:

  Value Name: MultipleUsersOnConnection
  Data Type:  REG_DWORD
  Value:      0

5. Quit Registry Editor.

Additional query words:

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Keywords          :  
Technology        : kbWinNTsearch kbWinNT400search kbWinNTSsearch kbWinNTS400search kbNTTermServ400 kbNTTermServSearch
Version           : winnt:4.0
Issue type        : kbprb

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