SnaBase and SNA Server Don't Accept New Client Connections

The information in this article applies to:

• Microsoft SNA Server, versions 3.0 and 3.0 Service Pack 1 (SP1)

SYMPTOMS

SnaBase and SNA Server may unexpectedly stop accepting new client connections after changes to the SNA Server configuration are saved using SNA Server Manager. Clients who are already connected through the SnaBase or server continue to function correctly. New clients may fail to get a sponsor connection, and will display one of the following error messages:

Windows NT client:

   SNA Server - ERROR # 1003
   SnaBase could not open a sponsor connection to server <server>

   SnaBase
   ERROR: Could not open sponsor connection to <server>

   SNA Server Error: 546 Cannot establish connection with SNA Server
   <servername>.

CAUSE

Under SNA Server 3.0, every time a 3.0 client opens the sponsor connection, the SnaBase makes a local remote procedure call (RPC) to check if the encryption flag is enabled for the user record. If this occurs while another thread of the SnaBase is notified of a configuration file change, an SnaBase deadlock can occur.

When the deadlock occurs, the DMOD critical section is held, preventing new users from connecting to either SnaBase or SNA Server.

NOTE: For information on other potential causes of client connection problems to SNA Server 3.0 servers, see the following articles in the Microsoft Knowledge Base:

   Article ID: Q168546
   Title     : Access Violation May Occur After Upgrading to 3.0 SP1

   Article ID: Q167196
   Title     : SNA Server 3.0 SP1 Update May Break Named Pipe Clients

STATUS

Microsoft has confirmed this to be a problem in SNA Server versions 3.0 and 3.0 Service Pack 1 (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):

   S E R V P A C K

MORE INFORMATION

With the fix applied, the asynchronous RPC requests done from the SnaBase DMOD are really asynchronous; without the fix, they are synchronous, which can cause a deadlock in certain situations.