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Q234843: RUI Application Receives Duplicate MSG10 Screen

Article: Q234843
Product(s): Microsoft SNA Server
Version(s): WINDOWS:3.0,3.0SP1,3.0SP2,3.0SP3,3.0SP4,4.0,4.0SP1,4.0SP2
Operating System(s): 
Keyword(s): kbsna400sp3fix kbsna300sp1 kbsna300sp2 kbsna300sp3 kbsna300sp4 sna4 kbsna400sp1 kbsna40
Last Modified: 06-AUG-2002

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The information in this article applies to:

- Microsoft SNA Server, versions 3.0, 3.0SP1, 3.0SP2, 3.0SP3, 3.0SP4, 4.0, 4.0SP1, 4.0SP2 
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IMPORTANT: This article contains information about modifying the registry. Before you 
modify the registry, make sure to back it up and make sure that you understand how to restore 
the registry if a problem occurs. For information about how to back up, restore, and edit the 
registry, click the following article number to view the article in the Microsoft Knowledge Base:

  Q256986 Description of the Microsoft Windows Registry

SYMPTOMS
========

If an RUI application is configured to open several instances of pooled LUA
sessions, SNA Server may receive a duplicate USSMSG10 (that is, VTAM Signon or
"banner") or USSMSG7 (VTAM error) screen on the SSCP-LU session under certain
timing conditions. This duplicate screen is then passed to the RUI application
during normal session cleanup. Receiving the additional SSCP-LU message may
cause problems for the application because it was not expecting to receive this
information twice. The actual symptoms experienced are application-specific
because it depends on how the application is designed.

NOTE: This problem is not limited to RUI applications and may occur with any
application that uses LUA or 3270 LU Pools.

CAUSE
=====

While rapidly deactivating and activating a dependent session, the SNA Server
may receive the host's USSMSG10 or USSMSG7 screen (intended for the previous
user) after SNA Server has sent a NOTIFY(SLU Enabled) message to activate the
session for the new user, along with another USSMSG10 screen for the new session
activation. Because SNA Server actually receives two SSCP-LU messages from the
host, the 3270 or LUA application receives both messages.

At this time, there has only been one reported instance of this problem because
under normal circumstances, a host does not send a USSMSG10 or USSMSG7 screen
after receiving a NOTIFY(SLU Disabled) during session cleanup.

RESOLUTION
==========

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

  Q215838 How to Obtain the Latest SNA Server Version 4.0 Service Pack


STATUS
======

Microsoft has confirmed that this is a problem in Microsoft SNA Server versions
3.0, 3.0 SP1, 3.0 SP3, 3.0 SP4, 4.0, 4.0 SP1, 4.0 SP2. This problem was first
corrected in SNA Server version 4.0 Service Pack 3.

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

SNA Server returns an LU to its pool for subsequent session requests after it
receives a NOTIFY(SLU Disabled) +RSP from the host in response to the NOTIFY(SLU
Disabled) that it sent to inform the host that the session has been terminated
by the application.

To prevent the duplicate MSG10 signon screen problem from occurring, a new
feature has been added to SNA Server to allow for a configurable delay before
returning an LU to its pool for use after a NOTIFY(SLU Disabled) +RSP has been
received.

In addition to applying the updated binaries, the following registry entry has to
be added to configure the amount of delay desired.

WARNING: If you use Registry Editor incorrectly, you may cause serious problems
that may require you to reinstall your operating system. Microsoft cannot
guarantee that you can solve problems that result from using Registry Editor
incorrectly. Use Registry Editor at your own risk.

1. Start Registry Editor (Regedt32.exe).

2. Locate the following key in the registry:

  HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\SnaServr\Parameters

3. On the Edit menu, click Add Value, and then add the following registry value:

  Value Name: SSCPDelay
  Data Type: REG_DWORD
  Value: <Delay in Seconds>

4. Quit Registry Editor.

The value entered is the time interval in seconds before an LU is released for
reuse in the pool. This is a global parameter that affects all 3270 and LUA
pools. If a five-second delay is specified, an LU will not be released for use
until five seconds after SNA Server receives the NOTIFY(SLU Disabled) +RSP for
this LU.

The following scenario was observed in the one reported instance of this problem
when using a multi-threaded RUI application:

1. An application thread issues an RUI_TERM to terminate a host session. The
  following shows the message flow between SNA Server and the host.

         SNA Server                        Host

         TRMSLF                ->
                               <-          TRMSLF +RSP
                               <-          UNBIND(Normal)
         UNBIND +RSP           ->
         NOTIFY(SLU Disabled)  ->
                               <-          NOTIFY +RSP

2. The RUI_TERM for this thread finishes.

3. Another thread issues an RUI_INIT against the same LU Pool at approximately
  the same time the first thread is issuing the RUI_TERM.

         NOTIFY(SLU Enabled)   ->
                               <-          MSG10 Screen
                               <-          NOTIFY +RSP
         +RSP                  ->
                               <-          MSG10 Screen
         +RSP                  ->

For additional information about a similar problem using RUI applications
receiving duplicate signon screens, please see the following article in the
Microsoft Knowledge Base:

  Q107384 RUI Interface Enhancement to Avoid Duplicate Signon Screens

NOTE: The INITDELAY parameter described in this article doesn't solve the problem
when using LUA pools because another application or thread in the same
application may still get in and observe this problem

Additional query words:

======================================================================
Keywords          : kbsna400sp3fix kbsna300sp1 kbsna300sp2 kbsna300sp3 kbsna300sp4 sna4 kbsna400sp1 kbsna400sp2 
Technology        : kbAudDeveloper kbSNAServSearch kbSNAServ300 kbSNAServ400
Version           : WINDOWS:3.0,3.0SP1,3.0SP2,3.0SP3,3.0SP4,4.0,4.0SP1,4.0SP2
Issue type        : kbbug
Solution Type     : kbfix

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