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Q160576: 3270 Sessions Unexpectedly Return to SSCP Screen

Article: Q160576
Product(s): Microsoft SNA Server
Version(s): WINDOWS:2.0,2.1,2.11,3.0,4.0
Operating System(s): 
Keyword(s): kbnetwork
Last Modified: 13-JUN-2001

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The information in this article applies to:

- Microsoft SNA Server, versions 2.0, 2.1, 2.11, 3.0, 4.0, on platform(s):
   - the operating system: Microsoft Windows NT 
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SYMPTOMS
========

SNA Server clients using 3270 display sessions are returned to the SSCP (VTAM
Signon) screen unexpectedly while actively working in a host application. The
SNA Server may log one or more of the following events in the Windows NT
Application Event Log when this problem occurs:

  Event ID: 4
  Source: SNA Server
  Description: (1133) Message Sequence Error

  EXPLANATION
  The SNA server (node) received an invalid or unexpected message from a
  remote node on an SNA session. The remote system has a possible
  configuration or internal logic error.

  SUBCODE INFORMATION
  X'1133' The node received a request with an invalid sequence number.

  Event ID: 12
  Source: SNA Server
  Description: (1118) Negative Response from Remote System (SENSE = 200D)

  SUBCODE INFORMATION
  X'1118' The local SNA server (node) received an SNA negative response
  on an SNA session from a remote system, which indicates a protocol
  violation by the 3270 emulator. The SNA sense code shown gives details
  of the type of error. See "IBM Systems Network Architecture: Formats"
  for an explanation of the sense code.

  Event ID: 13
  Source: SNA Server
  Description: (1141) Message Sequence Error (SENSE = 2001)

  EXPLANATION
  The SNA server (node) received an invalid or unexpected message from a
  remote node during an SNA session. The cause is probably a logic error
  in the remote system. The SNA sense data shown gives details of the type
  of error.

  SUBCODE INFORMATION
  X'1141' Session-level protocol violation in an SNA message from the
  partner
  LU.

CAUSE
=====

This has only been reported on SNA Servers with 802.2 connections to IBM 3174
Control Units on Ethernet networks. The problem occurs because a 3174 Ethernet
gateway may send a duplicate SNA sequence number to the SNA Server when the 3174
is handling an SNA frame between 1490 and 1493 bytes in size. This leads to a
condition where a frame may be re-sent by the 3174 causing the symptoms
discussed previously. In addition, the problem only occurs if the 3174 is
running 3174 Microcode Level C6.1 or C6.2.

RESOLUTION
==========

A fix for this problem is available from IBM. Contact IBM support and request
IBM 3174 PTR #B27E.

MORE INFORMATION
================

For information about how to contact IBM, query in the Knowledge Base for one of
the following articles:

  Q65416 Hardware and Software Third-Party Vendor Contact List, A-K

  Q60781 Hardware and Software Third-Party Vendor Contact List, L-P

  Q60782 Hardware and Software Third-Party Vendor Contact List, Q-Z


The third-party products discussed here are manufactured by vendors independent
of Microsoft; we make no warranty, implied or otherwise, regarding these
products' performance or reliability.

Additional query words: prodsna

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Keywords          : kbnetwork 
Technology        : kbAudDeveloper kbSNAServSearch
Version           : WINDOWS:2.0,2.1,2.11,3.0,4.0

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