Article ID: 134905
Article Last Modified on 12/8/2003
APPLIES TO
- Microsoft SNA Server 2.0, when used with:
- Microsoft Windows NT 4.0
- Microsoft SNA Server 2.1, when used with:
- Microsoft Windows NT 4.0
- Microsoft SNA Server 3.0, when used with:
- Microsoft Windows NT 4.0
This article was previously published under Q134905
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:
256986 Description of the Microsoft Windows Registry
SYMPTOMS
When you use the SNA Server client named pipe interface to communicate with an SNA Server running on Windows NT Server 3.5, the following error may appear in the Windows NT system log:
This error is logged by the Windows NT server service when an SNA Server client named pipe session is lost unexpectedly. This error occurs more readily with SNA Server named pipe-attached clients than it does with other named pipe applications (such as SQL Server) because the SNA client software always posts a named pipe read request against the server. If a session error occurs with the read request outstanding, the Windows NT server logs event 2012.
This error indicates that a client-server LAN session was lost, causing the user to lose their SNA session. This article describes the most common causes of this error.
STATUS
Microsoft has confirmed that this is a problem in the Microsoft products that are listed at the beginning of this article.
MORE INFORMATION
Event 2012 commonly occurs when:
- You are using Windows for Workgroups 3.11 and have not installed update Windows for Workgroups files.
There is named pipe disconnect problem in Windows for Workgroups 3.11. To correct this problem, upgrade to the Windows for Workgroups 3.11 client files included on the Windows NT 3.5 or 3.51 CD-ROM. - Your client computer is running Windows NT 3.5 and you have not installed the fixed RDR.SYS file.
When you use Windows NT 3.5 clients to communicate with SNA Server, a problem in the RDR.SYS file can cause the network session to be lost when exiting an SNA Server Windows NT client application. To correct this problem, upgrade to Windows NT 3.51, or install the latest U.S. Service Pack for Windows NT 3.5.
For information on obtaining the Service Pack, query on the following word in the Microsoft Knowledge Base (without the spaces):S E R V P A C K
For more information on this problem, please see the following article in the Microsoft Knowledge Base:
126451 SNA Server: Windows NT Client Loses Session To Server
- You turn off client computers
If you turn off a client computer while an SNA Server named pipe session is active, error 2012 may be logged. - You have underlying network problems.
As with any client-server LAN session, the session can be lost if there are underlying network problems occurring in the LAN. Problems can occur if there is a bridge fault, router fault, or media failure.
To troubleshoot this problem, create a general network sniffer trace or Microsoft Network Monitor trace to determine whether underlying LAN errors are occurring. If so, identify and correct the problems. - You have a shortage of Windows NT 3.5 Server Message Block (SMB) buffer space.
When you connect over 100 - 150 SNA Server clients using the Microsoft N Networking (named pipe) client interface, you may run out of Windows NT 3.5 SMB buffer space.
The Windows NT 3.5 Server service supports up to 512 maxworkitems. Maxworkitems are a server resource used to support data exchange with clients, including named pipe applications such as SNA Server. Because the SNA Server client software may have more than one named pipe session open with the server, and a read request is always posted on each named pipe, the Windows NT 3.5 server can run out of resources required to process the SNA Server named pipe client traffic. This can lead to slow SNA client performance and lost client sessions.
NOTE: The Windows NT 3.5 server service normally sets the maxworkitems resource to 512 (decimal), the recommended setting for SNA Server, when the Windows NT Server is configured to "maximize throughput for network applications." However, due to a problem with the "NET CONFIG SERVER" command, it is possible that your MaxWorkItems registry setting is set to a value lower than 512, causing an SMB buffer shortage to occur. For more information on this problem, please see the following article in the Microsoft Knowledge Base:128167 Server Service Configuration and Tuning
If the Windows NT 3.5 MaxWorkItems setting is already set to 512 decimal, either of the following two workarounds may help you resolve the problem:
- Switch the SNA Server clients to use an interface other than named pipes (for example, TCP/IP sockets). The new interface should not use the Windows NT server and should bypasses the need for work items. However, this workaround requires the SNA client user perform an additional login to the Windows NT server during SNA client startup. This is necessary to enforce Windows NT security.
NOTE: Although SNA Server 2.1 does provide some capability to automate the additional client login, this functionality has been further enhanced in SNA Server 2.11. For more information, please see the following article in the Microsoft Knowledge Base:130854 Automating the SNA Server Win 3.x Client Login Process
- To connect larger numbers of SNA Server clients and continue using the named pipe interface, upgrade to Windows NT 3.51 so you can increase MaxWorkItems setting:
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.
- Upgrade to Windows NT 3.51.
- Run Registry Editor (REGEDT32.EXE).
From the HKEY_LOCAL_MACHINE subtree, go to the following key:
\SYSTEM\CurrentControlSet\Services\LanmanServer\Parameters- Set MaxWorkItems to 4096:
MaxWorkItems: REG_DWORD: 4096 (decimal)
In simulated client testing, over 1500 SNA Server named pipe clients were able to connect to a single SNA Server using this setting.
NOTE: SNA Server 2.11 also includes optimizations that reduces the memory allocation for named pipe connections, which lessen the use of Windows NT Server SMB buffers. However, Microsoft recommends you upgrade to Windows NT 3.51 to connect large numbers of SNA Server clients if the named pipes interface is required.
This registry setting must be set manually when using SNA Server 2.1. If SNA Server 2.11 is installed on a server running Windows NT 3.51, SNA Server 2.11 Setup sets this parameter to 4096.
- Switch the SNA Server clients to use an interface other than named pipes (for example, TCP/IP sockets). The new interface should not use the Windows NT server and should bypasses the need for work items. However, this workaround requires the SNA client user perform an additional login to the Windows NT server during SNA client startup. This is necessary to enforce Windows NT security.
Additional query words: prodsna 2.00 2.10 2.11 3.50 3.51 event viewer
Keywords: kbbug KB134905
