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Microsoft KB Archive/101235

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Knowledge Base

TN3270 Server Now Supports Client-Side Hot Backup

Article ID: 101235

Article Last Modified on 6/13/2001


  • Microsoft SNA Server 3.0

This article was previously published under Q101235


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.


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.


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:


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.


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):


Additional query words: prodsna

Keywords: kbinterop kbnetwork KB101235