SNA Server and 2012 System Log Errors

MORE INFORMATION

• 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.
    
    
    1. Upgrade to Windows NT 3.51.
    2. Run Registry Editor (REGEDT32.EXE).
    3. From the HKEY_LOCAL_MACHINE subtree, go to the following key:

       \SYSTEM\CurrentControlSet\Services\LanmanServer\Parameters
       									

    4. 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.
       
       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.
       
       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.