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Crossing the Channel: High-Speed File and Print Distribution With or Without an SNA Gateway.

You may not need an SNA gateway if file and print distribution is your primary goal.

Accessing the Mainframe

In popular role-playing games, secret passageways or portals sometimes present themselves. Whether you should take the passageway or not depends on your skill level and what you are trying to do. A similar principle applies to access methods in host connectivity scenarios. For some companies or departments, interactive access to mainframe-based data and applications necessitates terminal emulation and Web-to-host integration. For such companies, an SNA gateway probably offers the most benefits.

For many organizations, however, legacy access is mostly limited to file and print distribution. These corporations can maximize their investments in existing mainframe data and applications by taking advantage of a little known method of mainframe access called ‘channel-to-channel’ connectivity, or CTC. CTC is the most efficient way of getting data into and out of the mainframe. It was originally developed by IBM prior to the development of the Systems Network Architecture (SNA), and it uses a sparse instruction set that simplifies mainframe access for certain applications, such as file and print distribution.

Best of all, CTC bypasses Virtual Telecommunications Access Method (VTAM), which processes all SNA traffic. Eliminating VTAM can result is faster data transfer rates and decreased response times for systems developed to exploit the advantages of CTC.

Direct Connection to the Mainframe Channel

One such system is Channel to Channel Network Job Entry (CTC-NJE), a hardware and software module of the Barr Enterprise Print Server, Barr Systems’ powerful complete host connectivity and print management solution. CTC-NJE leverages the speed and efficiency of a direct channel connection to the mainframe to support the most powerful job entry system available in the mainframe world, Network Job Entry (NJE). NJE, a peer-to-peer host communications protocol, allows job headers containing important routing and processing information for use in distributed printing, document management, and archival and retrieval systems.

Channel-Attached SNA Gateway

But what if you require an SNA gateway, or already have one in place? There’s no need for you to be left behind, since channel technology can help you maximize the investment in your SNA gateway. In order to achieve the ultimate performance for your SNA gateway users, connecting the gateway directly to the mainframe channel is the configuration of choice. Mainframe channel connections support channel speeds of up to 17 MBps with ESCON. This is a substantial increase over alternative connection speeds, and it can dramatically improve performance for every connected user.

Many companies are moving toward implementing TCP/IP and eliminating SNA protocols from the backbone network. When the SNA gateway is channel-attached, the SNA protocol can be isolated strictly to the data center, using TCP/IP as a common backbone. With the benefits of increased speed, more users, greater security and reliability, reduced costs and centralized management, it is easy to see why channel-attached SNA gateways are the configuration of choice in the industry.

Implementing an SNA gateway is an involved process that may involve changes on the host. Barr consultants are among the best in the industry, and they are ready to assist in any way.

Pass-Through TCP/IP

Whether you have an SNA gateway or not, there's one channel connectivity strategy that always works—if you have implemented a TCP/IP stack on your mainframe. It’s TCP/IP pass-through, and it allows you to attach your servers and applications either directly to the mainframe channel or via the SNA gateway while supporting familiar file transfer and terminal emulation applications, such as TN3270E, TN5250E, and FTP. This support typically involves use of an IBM 3172 Interconnect Controller, which is limited to 90 MHz processor speeds. Barr Systems provides 3172 emulation at server processor speeds by supplying advanced hardware and software solutions that lead the industry.


Enterprise information systems managers and executives recognize the importance of leveraging their legacy data for enterprise-wide print distribution, reporting, Web-to-host, enterprise resource planning, and many other modern business strategies. Using advanced channel technology, Barr Systems leads the industry in providing solutions for companies who want to play an important role in defining success in the coming decades.

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