KnowledgeBase Archive

An Archive of Early Microsoft KnowledgeBase Articles

View on GitHub

Q275469: APPC Load Balancing May Fail to Choose "Best" SNA Server

Article: Q275469
Product(s): Microsoft SNA Server
Version(s): 4.0,4.0 SP1,4.0 SP2,4.0 SP3
Operating System(s): 
Keyword(s): sna4 kbsna400sp1 kbsna400sp2 kbsna400sp3 kbSNA400sp4fix kbSNA400PreSP4fix
Last Modified: 12-JUN-2001

-------------------------------------------------------------------------------
The information in this article applies to:

- Microsoft SNA Server, versions 4.0, 4.0 SP1, 4.0 SP2, 4.0 SP3 
-------------------------------------------------------------------------------

SYMPTOMS
========

An Advanced Program-to-Program Communications (APPC) or Common Programming
Interface for Communications (CPI-C) application may not connect to a SNA Server
that has the best chance of providing a LU 6.2 session over the specified APPC
Local LU/RemoteLU/Mode. As a result, the application may not be able to obtain
an available LU 6.2 session or the application may experience a delay while
finding a SNA Server with an available LU 6.2 session.

The symptoms that are experienced by an end user who is running the APPC or CPI-C
application may vary.

CAUSE
=====

The APPC library locates an available LU 6.2 session that matches the parameters
(Local APPC LU and Remote APPC LU, for example) that are requested by the
application. If there are multiple SNA Server computers that can provide the
requested Local and/or Remote APPC LUs, the APPC Library contacts the SNA Server
computers in a random order according to how the servers are listed in the SNA
Client's Service Table. The SNA Server computer can respond to the session
requests with various errors depending on the state of its configured
connections and the availability of the LU 6.2 sessions on those connections.

When the APPC Library receives these error responses from the available SNA
Server computers, the errors are ranked to determine which SNA Server computer
has the greatest probability of providing the requested LU 6.2 session.

The problem described here occurs because the errors that are returned by the SNA
Servers are giving priority to SNA Servers that have a lower chance of being
able to satisfy the session request than other SNA Servers that have a better
chance of satisfying the request.

NOTE: This problem occurs only when the application specifies a specific Local
APPC LU in the TP_STARTED request. If the application specifies a "blank" Local
APPC LU in the TP_STARTED request, this problem does not occur.


RESOLUTION
==========

To resolve this problem, obtain the latest service pack for SNA Server 4.0. For
additional information, please see the following article in the Microsoft
Knowledge Base:

  Q215838 How to Obtain the Latest SNA Server Version 4.0 Service Pack



STATUS
======

Microsoft has confirmed this to be a problem in Microsoft SNA Server version
4.0, 4.0 SP1, 4.0 SP2, 4.0 SP3.

This problem was first corrected in SNA Server 4.0 Service Pack 4.


Additional query words:

======================================================================
Keywords          : sna4 kbsna400sp1 kbsna400sp2 kbsna400sp3 kbSNA400sp4fix kbSNA400PreSP4fix 
Technology        : kbAudDeveloper kbSNAServSearch kbSNAServ400 kbSNAServ400SP1 kbSNAServ400SP2 kbSNAServ400SP3
Version           : :4.0,4.0 SP1,4.0 SP2,4.0 SP3
Issue type        : kbbug
Solution Type     : kbfix

=============================================================================

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY.