3270 Sessions Unexpectedly Return to SSCP Screen

• Microsoft SNA Server, versions 2.0, 2.1, 2.11, 3.0
  on the following platforms: NT

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

Additional query words: prodsna

Keywords : kbnetwork sna3rdparty sna3270 snadlc
Version : WINDOWS:2.0,2.1,2.11,3.0
Platform : WINDOWS
Issue type :