APPC/CPI-C Applications May Hang When Allocating LU 6.2 Sessions (193684)

SYMPTOMS

An APPC or CPI-C application may occasionally fail to establish a session after a host system (Mainframe or AS/400) initiates the Change Number of Sessions (CNOS) negotiation.

Applications may exhibit different symptoms if this occurs, depending on how the application is written. If the application has timeout, the application will terminate the session after the timeout has been reached. Applications that do not have a timeout may appear to hang (stop responding) while waiting for the Allocate call to complete.

This problem did not occur with SNA Server 3.0 SP1 and earlier.

CAUSE

This problem can occur when the host system initiates CNOS negotiation with the SNA Server. When this occurs, suspended LU 6.2 sessions are in an unusable state by SNA Server, causing application-generated Open LU 6.2 Requests (for example, ALLOCATEs) to hang.

CNOS negotiation is not commonly initiated by the host system. SNA Server usually initiates CNOS negotiation because of application requests for LU 6.2 sessions, or because the SNA Server is configured to auto activate LU 6.2 sessions. Therefore, occurrences of this problem are not common.

This problem was exposed due to a change included in SNA Server 3.0 SP2 to correct the problem described in the following Knowledge Base article:

170070 SNA Client Allocate Requests May Hang After AS/400 IPL

RESOLUTION

SNA Server 3.0

To resolve this problem, obtain the latest service pack for SNA Server version 3.0. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:

184307 How to Obtain the Latest SNA Server Version 3.0 Service Pack

SNA Server 4.0

Microsoft has confirmed this to be a problem in SNA Server version 4.0 and 4.0 SP1. This problem was corrected in the latest SNA Server version 4.0 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

STATUS

Microsoft has confirmed that this is a problem in SNA Server versions 3.0SP2, 3.0 SP3, 4.0, and 4.0 SP1. This problem was first corrected in SNA Server 3.0 Service Pack 4.