Setting Up Microsoft BackOffice 2.0 (Part 3)

snaserver2-iconThroughout the 1970s and 80s, computer terminals such as the IBM 3270 crept up in office environments allowing staff to easily retrieve data from the company’s mainframe. Mainframes tend to come with a hefty price tag and due to significant investment and mission-critical functions, are subject to much less frequent changes. Whilst the computer terminals gradually were replaced with PCs, the mainframes often remained. The protocol for communications lived on (e.g. as TN3270E) allowing emulation of the original computer terminals themselves.

In Part 3 I’ll be checking out Microsoft SNA Server included with BackOffice 2.0, following from Exchange Server and Internet Information Server some time ago. SNA refers to IBM’s proprietary Systems Network Architecture dating back to 1974. SNA Server was superseded by Microsoft with Host Integration Server in the early 2000s.

SNA Server 2.11

The role of SNA Server is primarily to work as a gateway between Windows based networks and mainframes (often by IBM), AS/400 mid-range servers and Unix systems, that were to be found in large corporate or government enterprises.


Shown in the diagram above, a possible use case scenario was to have a bunch of Windows-based office PCs connected on a domain using the TCP/IP network protocol. The domain controller is running Windows NT 3.51 Server with SNA Server installed. SNA Server is then configured to connect to an IBM mainframe using the X.25 protocol. Consequently the office PCs could then use terminal emulation software to interact with the mainframe. Conversely information from the mainframe can be directed to the office printer.

Client terminal applications such as Relay/PC Gold and Reflection did allow direct connection to the mainframe from the PC. The attraction to SNA Server however is simplifying the administrative burden for IT departments by centralising connection points and user permissions.

Commencing installation from the BackOffice Installer, Setup was quick to notify this was an evaluation copy of SNA Server 2.11 that allowed for only five concurrent users. As BackOffice was aimed for small business, connecting to mainframes was likely unnecessary but was enough to entertain functionality for those considering it. From what I gathered a regular license was $409 US per server, in addition to $64.95 US per user license. Based on that it was quite a bit cheaper than Version 3.0 in hindsight.


Evaluation only.

Continuing on Setup detects what network protocols are installed on your server, and allows you to select which ones SNA Server is to work with. The complete options are Microsoft Networking (Named Pipes), Novell Netware (IPX/SPX), Banyan VINES, TCP/IP, and AppleTalk.

Next confirmation will pop up about a SNA Server domain name. This was a new feature with Version 2.11 in that it was now possible to have several SNA Server sub-domains under a Windows NT domain.

The server role is then requested, selecting either to be the Primary Configuration Server, Backup Configuration Server, or Member Server with no configuration. Primay and backup roles operate in a similar manner to primary and secondary domain controllers on a network in function, though hold a domain-wide configuration file. The configuration file holds sub-domain information such as the SNA servers, link services, and user information. For each sub-domain there can only be one Primary Configuration Server, though it’s possible to have up to 49 Backup Configuration Servers.

Near the end of installation, the remaining piece is to select and configure link services. This determines the protocol/s to ultimately talk between the NT server and mainframe or other desired system, provided the right hardware adapter is installed.


Configuring a X.25 link.

As Setup completes, the following program group is presented in Program Manager.


SNA Server in Program Manager.

Initially administrators will seek SNA Server Admin where it’s split into three focus points. The Servers and Connections window is fairly self explanatory in that it manages SNA servers within an NT domain, and their connections to a SNA network and its systems. Connections can be easily transferred to other SNA servers as required. Users and Groups links directly with those from the NT domain.

Bridging these together is by incorporating logical units. A logical unit (LU) in short identifies and holds configuration information of users and devices to establish a session onto the SNA network. Variations can occur in the type of connection and terminal emulation for each logical unit.

Logical units of the same kind can be grouped together as a logical unit pool. Some of the benefits of incorporating a pool is to act as a fail-safe in case one of the logical units fails (e.g. one of the SNA servers goes out of service), and balancing the load from users over multiple servers.



Administer servers, connections, and users.

When it comes to SNA, I’m far from being an expert but can somewhat relate. During the 2000s, working in the telecommunications industry I had been using a 3270 terminal emulator to connect to the mainframe that managed telephone lines and billing. One thing that was certain compared to newer web-based systems was that it had rock solid stability. Not once did I experience an outage, nor the need for frequent software updates.

2 thoughts on “Setting Up Microsoft BackOffice 2.0 (Part 3)

  1. Neozeed says:

    There should be a SDLC ‘demo’ link that’ll at least flash some text up on a 3270…

    Also there is a Hercules experimental patch to add DLSw… A cisco router can ‘proxy’ between SNA and DLSw so I’ve been told. I haven’t set it up, but it very well maybe possible to get SNA server talking to a ‘mainframe’…. I just don’t know enough about MVS to sysgen.


  2. chiaki says:

    ah i saw this stuff in action on VHS-tape for developer (ad or training?) that shows all the fancy new features in NT 3.5.
    in one scene bill gates connected to the MS AS/400 and show how easily he can get the data from DB2 per 5250-emulator and paste it to excel!


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