DOCUMENT:Q275469 12-JUN-2001 [sna] TITLE :APPC Load Balancing May Fail to Choose "Best" SNA Server PRODUCT :Microsoft SNA Server PROD/VER::4.0,4.0 SP1,4.0 SP2,4.0 SP3 OPER/SYS: KEYWORDS:sna4 kbsna400sp1 kbsna400sp2 kbsna400sp3 kbSNA400sp4fix kbSNA400PreSP4fix ====================================================================== ------------------------------------------------------------------------------- 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. Copyright Microsoft Corporation 2001.