Microsoft KB Archive/169204

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Knowledge Base

Renegotiate CNOS After Connection Reestablishment

Article ID: 169204

Article Last Modified on 6/24/2004


  • Microsoft SNA Server 2.11 Service Pack 2
  • Microsoft SNA Server 4.0

This article was previously published under Q169204


CNOS (change number of sessions) is a general data stream (GDS) variable that is used to negotiate the number of sessions that can be used between an LU-LU pair. This takes place during connection startup after the SNA Server service has started. If the connection is stopped (without stopping the SNA Server service), and then restarted, CNOS is not renegotiated.

NOTE: There are other cases where CNOS is renegotiated. These are outlined in the "Registry Entries Only Used on an SNA Server" section of the "SNA Server Reference Guide."


Microsoft has confirmed this to be a problem in SNA Server versions 2.11 Service Pack 2 (SP2) and 3.0 SP1. This problem was corrected in the latest SNA Server version 3.0 U.S. Service Pack. For information on obtaining this Service Pack, query on the following word in the Microsoft Knowledge Base (without the spaces):



With the fix applied, Snaservr.exe renegotiates CNOS after a connection is stopped and restarted without ever bringing down the SNA Server service. In addition, after you apply the fix, you need to edit the registry as described below.

WARNING: Using Registry Editor incorrectly can cause serious, system-wide problems that may require you to reinstall Windows NT to correct them. Microsoft cannot guarantee that any problems resulting from the use of Registry Editor can be solved. Use this tool at your own risk.

  1. Start Registry Editor (Regedt32.exe or Regedit.exe, as appropriate for your version of Windows NT).
  2. Go to the following key in the registry:

          HKEY_LOCAL_ MACHINE\System\CurrentControlSet\Services\ 
  3. On the Edit menu, click Add Value and use the following entry:

    Value Name: RenegCNOSAtReconnect
    Data Type: REG_SZ
    Value: YES

  4. Exit Registry Editor.

Keywords: kbbug kbfix kbnetwork KB169204