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FIX: The TN3270E emulator stops responding after issuing a logoff command from a host application

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Symptoms

The following are two possible scenarios that can occur when a user issues a logoff command to exit a mainframe application:

Scenario 1

After a user logs off from a host application, the TN3270 server receives the USS MSG10 screen from the host, and then the server returns to the IBM mainframe a negative response that includes the IBM Sense Code X'2004'.

From the user's perspective, the symptoms generally appear as a blank screen on the TN3270E emulator after the successful host application logoff. You expect the USS MSG10 screen to appear so that the user can log on to another host application.

Scenario 2

After a user logs off from a host application, the TN3270E emulator displays the following error message:
TN3270E Service Error 520

Internal LU session state error in
FirstInboundByteProcess.
State error id - 3 (expected CONT,RCV).
Current state - SSCP-LU, SNDNXMT
The following event is also logged in the application event log on the Host Integration Server 2000 server where the TN3270 server is running:


Event ID: 603
Source: TN3270 Server
Description:
TN3270(E) session with client at TCP/IP Address (port port number) using LU LU Name terminated abnormally because:
TN3270E Service Error 520
Internal LU session state error in FirstInboundByteProcess.
State error id - 3 (expected CONT,RCV).
Current state - SSCP-LU, SNDNXMT

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Cause

Scenario 1

This first problem scenario occurs when the TN3270 server receives an UNBIND request from a host application while waiting for an acknowledgment from a TN3270E emulator for data that the host application had sent before the UNBIND.

If the acknowledgment from the TN3270E emulator is received after UNBIND is received from the host application, the TN3270 server correctly discards the acknowledgment. The TN3270 server then incorrectly changes its internal session state for this host session. The change in the session state causes the TN3270 server to reject the USS MSG10 screen with IBM sense code X'2004'.

Scenario 2

The second problem scenario occurs when a TN3270E emulator sends 3270_LU_DATA over a SSCP_LU session. The host session transitions from a LU-LU session to a SSCP-LU session when a user logs off the mainframe application. The TN3270 server only expects to receive SSCP_LU_DATA from a TN3270E client when the host session is in an SSCP_LU state. The TN3270 server incorrectly changes its internal session state when it received 3270_LU_DATA over a SSCP-LU session. When this problem occurs, the TN3270 server logs the Event 603 error message and sends a TN3270E Service Error 520 message to the TN3270E emulator when the emulator receives additional data from the TN3270E emulator.

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Resolution

Service pack information

To resolve this problem, obtain the latest service pack for Microsoft Host Integration Server 2000. For more information, click the following article number to view the article in the Microsoft Knowledge Base:
328152� How to obtain the latest service pack for Host Integration Server 2000

Hotfix information

The English version of this hotfix has the file attributes (or later file attributes) that are listed in the following table. The dates and times for these files are listed in coordinated universal time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time tool in Control Panel. 
   Date         Time   Version    Size     File name
   ----------------------------------------------------
   13-Jun-2003  18:54  5.0.0.917  258,320  Tn3servr.exe
NOTE: Because of file dependencies, the most recent fix that contains the preceding files may also contain additional files.

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Status

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

This problem was corrected in Microsoft Host Integration Server 2000 Service Pack 2.

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More information

Scenario 1

The following series of events shows the data flow that results in the first problem scenario:
  1. The user issues a command to log off from a host application.
  2. The host application sends a data message that confirms the application logoff. The data message requires a response.
  3. The TN3270 server sends the data message to the TN3270E emulator. The TN3270 server expects to receive an acknowledgment to this data message.
  4. The host application does not wait for a response to the previous data message and sends an UNBIND to complete the logoff sequence.
  5. The TN3270 server receives the UNBIND message and sends the UNBIND message to the TN3270 emulator.
  6. The TN3270 server receives the acknowledgement to the initial data message.
  7. The TN3270 server discards the acknowledgement because it has already received an UNBIND for the session.
  8. The host sends a USS MSG10 screen.
  9. The TN3270 server rejects the USS MSG10 screen. This results in a -RSP response being sent to the host with IBM sense code X'2004'.

Scenario 2

The following series of events shows the data flow that results in the second problem scenario:
  1. The user issues a command to log off from a host application.
  2. The host application sends a data message that confirms the application logoff.
  3. The TN3270 server sends the data message to the TN3270E emulator.
  4. The host application sends an UNBIND message to the TN3270E emulator. After the UNBIND, the LU-LU session is terminated and a SSCP-LU session remains between the LU and the host system.
  5. The host system sends an USS MSG10 screen to the TN3270E emulator.
  6. The TN3270E emulator incorrectly sends 3270_LU_DATA to the TN3270 server. The server discards the message. The TN3270 server incorrectly changes its internal session state at this point.
  7. The TN3270E emulator then sends valid SSCP_LU_DATA to the TN3270 server. This message causes the TN3270E Service Error 520 error to be sent to the TN3270E emulator.
For more information about IBM sense codes, see the IBM SNA Formats (GA27-3136) manual. The third-party products that are discussed in this article are manufactured by companies that are independent of Microsoft. Microsoft makes no warranty, implied or otherwise, regarding the performance or reliability of these products.

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Keywords: KB822830, kbhotfixserver, kbqfe, kbfix, kbbug

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Article Info
Article ID : 822830
Revision : 4
Created on : 10/26/2005
Published on : 10/26/2005
Exists online : False
Views : 497