Microsoft KB Archive/158213

= Improve LU6.2 Load Balancing if NOINITCNOS Is Used =

Article ID: 158213

Article Last Modified on 11/26/2003

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APPLIES TO


 * Microsoft SNA Server 2.0
 * Microsoft SNA Server 2.1
 * Microsoft SNA Server 3.0
 * Microsoft SNA Server 2.11 Service Pack 1

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This article was previously published under Q158213





SYMPTOMS
When an APPC application tries to allocate a conversation specifying an LU/LU/mode partnership (using independent LU6.2), the SNA client APPC interface may queue the request against an SNA Server that has all available LU6.2 sessions in use. This may happen even if an SNA Server is in the domain that may have a suitable LU/LU/mode partnership defined, but which has not yet completed Change Number of Sessions (CNOS) negotiation. This can cause an application to wait for an available session to become free, instead of forcing another SNA Server to initiate a new LU/LU session to be used by the application.

Under SNA Server version 2.11, the following conditions can cause an independent LU 6.2 partnership to not complete CNOS negotiation:
 * If the NOINITCNOS registry setting is enabled on the SNA Server (this setting is documented in Appendix C of the SNA Server "Reference Guide".
 * If the SNA Server receives an error after sending a BIND request on the Local APPC LU/Remote APPC LU/SNASVCMG mode. SNA Server will log an Event 18 when this occurs.

For additional information, please see the following article in the Microsoft Knowledge Base:

150959 Preventing Repeated APPC Session Activation Failures Event 18



CAUSE
If an LU-LU pair has not completed CNOS negotiation, the SNA Server was returning an Open(LU6.2) response error of Err1=0/Err2=1F04. This caused the SNA client APPC interface to try a different server for a conversation.



RESOLUTION
To workaround this problem, the NOINITCNOS setting should not be used.

A hotfix is available for this problem, if you want to use the NOINITCNOS setting. The hotfix causes SNA Server to return an Err1=0/Err2=0004 to an Open(LU6.2) request if no CNOS negotiation has been completed for an independent LU/LU partnership. This causes the SNA client APPC interface to retry this server for a conversation, if no other servers have an available session.



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. This problem was corrected in the latest Microsoft SNA Server 2.11 U.S. Service Pack. For information on obtaining the service pack, query on the following word in the Microsoft Knowledge Base (without the spaces):

S E R V P A C K

Additional query words: sp1 prodsna

Keywords: kbbug kbfix KB158213

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