DOCUMENT:Q101235  13-JUN-2001  [sna]
TITLE   :TN3270 Server Now Supports Client-Side Hot Backup
PRODUCT :Microsoft SNA Server
PROD/VER:WINDOWS:2.11
OPER/SYS:
KEYWORDS:kbinterop kbnetwork

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The information in this article applies to:

 - Microsoft SNA Server, version 2.11 
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SYMPTOMS
========

If all the resources are in use on the SNA Server 2.11 TN3270 server the
Hot-Backup feature of some TN3270 emulators does not work.

The Hot-Backup feature, implemented in some TN3270 emulators, allows you to
specify the IP addresses of several TN3270 Servers for the emulator to attempt
to connect to. If access is denied it attempts to connect to the next IP address
specified.

CAUSE
=====

The SNA Server TN3270 Server always listens on a socket, allowing an emulator to
connect (that is, it fails to deny the socket connection), even if all of the
configured resources on the server are in use causing it not be able to service
that connection. When the emulator successfully opens a socket connection to one
of the addresses, in this case the address of the SNA Server TN3270 Server, the
emulator is locked into that address and cannot try another IP address specified
with the Hot-Backup feature.

RESOLUTION
==========

Microsoft has enhanced the SNA Server 2.11 files, TN3SERVR.EXE and TN3NTMSG.DLL,
to fully support the Hot-Backup feature of TN3270 emulators.

This update supports the option to stop listening once all of the configured SNA
resources are in use, and to start listening again once some become available.
This feature is turned on by setting the following registry entry under the
HKEY_LOCAL_MACHINE subtree under the following subkey:

   \CurrentControlSet\Services\TN3270\Parameters\CloseListenSocket

Type:  RG_EXPAND_SZ
Value: YES

In SNA Server 3.0 (and future SNA Server 2.11 service packs beyond SP1), the
CloseListenSocket option must be set to "ON". The administration tool has been
updated to support configuration of this parameter, so manual adjustment of the
registry is not necessary. If this setting is not configured or is set to any
other value, then the TN3270 Server does not stop listening.

STATUS
======

This feature is included in the latest U.S. Service Pack for SNA Server for
Windows NT, version 2.11. For information on obtaining the Service Pack, query
on the following word in the Microsoft Knowledge Base (without the spaces):

   S E R V P A C K

Additional query words: prodsna

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Keywords          : kbinterop kbnetwork 
Technology        : kbAudDeveloper kbSNAServSearch kbSNAServ211
Version           : WINDOWS:2.11

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