SNA Client Allocate Requests May Hang After AS/400 IPL

The information in this article applies to:

• Microsoft SNA Server for Windows NT, version 2.11, 2.11 SP1 & SP2, 3.0, 3.0 SP1

SYMPTOMS

If an APPC or CPIC application issues several conversation startup requests (that is, [MC_]ALLOCATE or CMALLC) immediately after an AS/400 IPL, some allocates may fail to complete, or complete after further client ALLOCATEs are issued.

This problem occurs after SNA Server renegotiates session limits for an LU/LU pair, where some pending client ALLOCATE requests are queued incorrectly and fail to be processed.

The symptoms of the problem may vary, based on the application being used. This problem would occur most commonly with an APPC or CPIC application which initiates many conversations concurrently to the same remote system (say, an AS/400 or CICS). It would be unlikely to occur when starting a single conversation (for example, 5250 emulation) on multiple client computers.

CAUSE

After the remote system is stopped and started (the AS/400 in this example), the existing session limits on all LU6.2 pairs have not been reset. If one or more users attempt to activate a new LU6.2 session at the same time, after the remote system has been reactivated, the remote system rejects the BIND request with sense code 08050000 (session limit exceeded), which causes SNA Server to reinitiate change-number-of-sessions (CNOS) renegotiation with the remote system.

The problem is that SNA Server was incorrectly queueing the user's initial activation requests after CNOS renegotiation had taken place, causing the client application to hang on the ALLOCATE request (for an APPC application) or CMALLC request (for a CPIC application).

RESOLUTION

An update to SNA Server 3.0 Service Pack 1 is available to correct this problem. The updated module is Snaservr.exe.

STATUS

Microsoft has confirmed this to be a problem in SNA Server version 2.11 (including SP1 and SP2) and SNA Server 3.0 (including 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

Keywords          : prodsna snaappc snacpic snaserverservice kbfix3.00.sp2 kbnetwork
Version           : 1.0
Platform          : WINDOWS
Issue type        : kbbug