Backup Config. Server May Not Always Read Local Config. File

The information in this article applies to:

• Microsoft SNA Server, versions 2.0, 2.1, 2.11, and 2.11 Service Pack 1

SYMPTOMS

If the SNA Server service is configured to start automatically on a backup configuration server and the SnaBase broadcast from the primary configuration server has not yet been received, SNA Server may read its configuration entries from another backup server's configuration file instead of the local Com.cfg file. This will likely cause no problems, but it may be inefficient.

If the SNA Server service encounters a network error while reading its configuration file entries from another backup server or from the primary configuration server, the following error occurs (though the Windows NT Server return code may vary):

   Event ID: 351
   Source:   SNA Server
   Description: Error trying to read from \\server\COMCFG\COM.CFG (rc=995)

This may indicate a problem with the underlying network. The above error occurred at a site where the primary configuration server was located across an IP router from the SNA Server. The IP router was acting as a "black hole router," which was causing the network session to fail abnormally. For more information on "black hole routers," see the following article in the Microsoft Knowledge Base:

   ARTICLE-ID: Q159211
   TITLE     : Diagnoses and Treatment of Black Hole Routers

CAUSE

When the SnaBase service starts on SNA Server, it listens for "service table" broadcast announcements from other SnaBase services running on other computers running SNA Server in the SNA subdomain. This broadcast message indicates the SNA Server services running on the server, the server's role in the SNA domain, and other attributes.

The SnaBase service (on backup and member configuration servers) keeps track of the "preferred" location for the SNA Server configuration file for the subdomain. When the SNA Server service starts, it reads its configuration entries from the configuration file located on the "preferred" server.

If a broadcast is received from the primary configuration server, then the primary server is always the preferred server. However, if the SnaBase has not yet heard from the primary configuration server, a remote backup server is chosen as the preferred server, instead of the local backup configuration file.

RESOLUTION

A backup configuration server now prioritizes the local Com.cfg file ahead of other backup configuration servers, if the primary configuration server announcement has not been received or if its SnaBase is not running.

STATUS

Microsoft has confirmed this to be a problem in Microsoft SNA Server versions 2.0, 2.1, 2.11, and 2.11 Service Pack 1. A supported fix is now available for SNA Server 2.11 Service Pack 1, but is not fully regression-tested and should be applied only to systems experiencing this specific problem. Unless you are severely impacted by this specific problem, Microsoft recommends that you wait for the next Service Pack that contains this fix. Contact Microsoft Technical Support for more information. receive Snadmod.dll