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Q163208: Downstream PU Fails to Activate After Short ACTLU Response

Article: Q163208
Product(s): Microsoft SNA Server
Version(s): WINDOWS:2.0,2.1,2.11,2.11 SP1
Operating System(s): 
Keyword(s): kbnetworkkbbuglist
Last Modified: 11-JUN-2002

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The information in this article applies to:

- Microsoft SNA Server, versions 2.0, 2.1, 2.11, 2.11 SP1 
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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
========

When a downstream PU2.0 emulator attempts to activate a session through an SNA
Server, SNA Server may never send a NOTIFY (available) request to the host,
causing the LU session to fail to activate.

This problem was observed when attempting to configure an ASCII-3270 protocol
converter (SyncResearch SDLC/LLC2 converter) to use an SNA Server downstream PU
connection.

CAUSE
=====

SNA Server automatically sends NOTIFY (unavailable) when the upstream host
connection becomes active, and it depends on the downstream PU2.0 client to send
a NOTIFY (available) or a "long" ACTLU response later on. However, some
downstream clients do not send a NOTIFY message and send "short" ACTLU
responses, and so SNA Server never sends a NOTIFY(available) to the host.

RESOLUTION
==========

An update to Snaservr.exe is available for SNA Server 2.11; the update supports
a new registry parameter to correct this problem. This update is newer than SNA
Server 2.11 Service Pack 1.

Once you have applied this update, you must also add the following registry
entry. This will cause SNA Server to respond to the downstream client connection
request. To add the registry entry:

WARNING: Using Registry Editor incorrectly can cause serious problems that may
require you to reinstall Windows NT. Microsoft cannot guarantee that problems
resulting from the incorrect use of Registry Editor can be solved. Use Registry
Editor at your own risk.

1. Start Registry Editor (Regedt32.exe).

2. Under the HKEY_LOCAL_MACHINE subtree, go to the following subkey:

     SYSTEM\CurrentControlSet\Services\SnaServr\Parameters

3. Tab to the right-hand window and press the <Insert> key. In the Add
  Value dialog box, type:

  Value Name: SHORTACTLU
  Data Type: REG_SZ

  and click OK.

4. In the String Editor dialog box, type:

  String: <any value>

  Once entered, the value will appear in REGEDT32 as follows:

  SHORTACTLU: REG_SZ: <any value>

5. Quit Registry Editor.

The SHORTACTLU registry entry causes SNA Server to respond to the downstream
client connection request the above behavior, regardless of the value the entry
is set to. When this registry entry is present, SNA Server sends a
NOTIFY(available) to the host when it receives a short ACTLU response from the
downstream client.

STATUS
======

Microsoft has confirmed this to be a problem in SNA Server versions 2.0, 2.1,
2.11, and 2.11 Service Pack 1 (this feature is implemented in 3.0).


A supported fix to 2.11 is now available, but has not been fully regression-
tested and should be applied only to systems experiencing this specific problem.
Unless you are severely impacted by this specific problem, Microsoft recommends
that you wait for the next Service Pack that contains this fix. Contact
Microsoft Technical Support for more information.



Additional query words: prodsna dspu

======================================================================
Keywords          : kbnetwork kbbuglist
Technology        : kbAudDeveloper kbSNAServSearch kbSNAServ200 kbSNAServ211 kbSNAServ210 kbSNAServ211SP1
Version           : WINDOWS:2.0,2.1,2.11,2.11 SP1
Issue type        : kbbug
Solution Type     : kbfix

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