Brief: The number of PCs connected to AS/400s has increased dramatically in recent years. At the same time, the equations that govern whether to use a Lan solution or a terminal emulation solution have also been changing. This article guides you through an analysis of why (or even if) PCs should be attached to your AS/400. The results will help you to determine which attachment method to use.
One of the most difficult choices for MIS managers who have PCs to attach to their AS/400 is deciding between a terminal emulation card solution or a local area network (LAN)-based one. This problem can be difficult to resolve due to its rather fuzzy nature. What are the strengths of a LAN? What about the costs associated with them? Does a definition of terminal emulation include PC Support? Which solution offers the most flexibility? ...the least cost? ...the most performance? In this article, I'll sort out these issues for you and give you grounds from which to make a rational, informed decision.
Defining the Problem
The point of this exercise is deceptively simple. You have numerous PCs in- house and have decided (or your user community has decided) that the PCs need to talk to your AS/400. Your first pass at the problem has yielded the following choices:
1. You can put terminal emulation cards in every PC, thereby allowing them to talk to the AS/400.
2. You can install a LAN, hook all the PCs into it and then attach that to the AS/400.
Which choice is for you? In order to determine the answer, we have to start with the basic issue of why your PCs need to connect to the AS/400! Many times I've had clients so caught up in the technology of the question that they've lost sight of the most important point of the whole issue: Why?
That question should bring to light the business reasons for connecting the PCs to the AS/400 in the first place. Connecting PCs to the AS/400 (or to each other, for that matter) for the sake of connection alone is dumb. Without a good, solid business reason, the PCs should be left alone.
Numerous articles deal with the technical side of corporate networking (see "Networking in the Corporate Climate," MC, June 1992); and while the technical issues are important, my contention is that they're pointless without sound business reasons behind them.
The following list of issues comprises 80 percent of the business requirements for connecting a PC to an AS/400:
o Common terminal access
o File transfer capabilities
o Resource sharing
o Electronic mail (E-mail)
Let's look at each of these in turn.
Common Terminal Access
Common terminal access can be defined as the ability to reach any application from any terminal. For example, many users want access to the AS/400 from their PCs to eliminate having both a PC and an AS/400 terminal on their desk. But an important issue presents itself at this point. Why a PC in the first place? If the reason you're connecting to your AS/400 is merely to create a common terminal access-a connection to the AS/400 with no PC tasks required at that location-stay with a terminal. The only reason to enter this emulator/LAN debate is if business needs require the PC.
If the situation does call for PCs, both terminal emulation cards and LANs can eliminate the clutter of devices on your desktop with ease. Terminal emulation cards make the AS/400 terminal unnecessary by allowing a PC to emulate an IBM terminal. LANs give your PC the functionality of an AS/400 terminal in one of two ways. In one method, the LAN routes requests for attachment to the AS/400 to a PC server containing software such as Novell's NetWare for SAA, which handles the LAN-to-AS/400 connection. In the second method, employed by traditional AS/400 LANs, the AS/400 acts as the server and contains the required token-ring or Ethernet protocol. The mechanisms are different, but the results are basically the same.
So, from the "I just need my PC to talk to the AS/400" perspective, the contest between the LAN and the terminal emulation card is basically a draw. Speed is probably the main difference. Normally, LAN protocols run at higher speeds (4-16Mbps) than standard AS/400 workstations support (around 1.2Mbps). The extent to which this affects response time depends on many factors, but if throughput is an important factor, LANs are generally more effective than terminal emulation. I'd caution you that speed for the sake of speed is not a sufficient business reason for selecting the LAN approach.
Other positive "side effects" of implementing common terminal access include centralizing E-mail, standardizing terminal types and configurations and eliminating duplicate communications links necessary for two tubes on one desk. These are the benefits which give weight to common terminal access as a legitimate business reason for entering the emulation/LAN debate.
File transfer issues in the midrange world are as old as the hills and five times as dusty. We've used everything from card decks (S/3) to diskettes (S/32, S/34 and S/36) to PC Support (S/36, S/38 and AS/400). Also on the scene are 2780 and 3780 RJE emulated card decks, and let's not forget magnetic tape and CD-ROM. Finally, we've all occasionally resorted to "Oh, the heck with it. Just rekey it on the other machine!"
Until recently, terminal emulation and file transfer were not the best of friends. The marketplace historically had a limited number of offerings, PC Support being chief among them. But nowadays, all vendors seem to have some sort of file transfer capability attached to their emulation card offerings. Some, of course, are better than others, but the net result is that most PCs with emulation cards can now transfer files with ease to the AS/400 and vice- versa.
Vendors normally add file transfer capabilities on to emulators-not quite as an afterthought, but let's face it...the main purpose of an emulator is to emulate, not to pass data. LANs were designed the other way around. LANs came into being, in large measure, for the express purpose of transferring data. It's one of the things they do best. In my opinion, LANs have an edge over terminal emulators in that their very design optimizes them for the transmission of data. This is one of the key distinctions between emulators and LANs.
Since the main purpose of LANs is the transfer of data, a LAN is not a good idea if file transfer is a rare occurrence at your installation. But if the "why" we discussed earlier contains the constant or repetitious transfer of data between users and the AS/400, LANs might be the answer.
The AS/400 can, in many cases, act as a server in the traditional client/server sense to hold data available to PCs. In this sense, the AS/400 be-comes a kind of library from which PC users check out data so that they can generate their own reports with PC-oriented software.
Certain types of LANs can use the AS/400 as a file server. With this type of setup, you wouldn't need to buy a separate file server; but the LAN is then forced into either a token-ring or Ethernet solution.
Connecting to the AS/400 means sharing physical resources, too. The data-rich nature of the midrange system practically ensures a regular backup regimen for data that might otherwise be stored on PCs with less rigorous backup procedures. Tapping into the AS/400's DASD supply may also minimize your PC hard disk requirements (at a higher cost, mind you). And finally, although PC printers generally offer more sophistication, AS/400 printers (which can be accessed through LANs or emulation) often provide the printing speeds a PC user might need to output an extremely long report.
As you take stock of resource-sharing issues, you may encounter other arguments masquerading as good business reasons for hooking up PCs to your AS/400. Related arguments frequently used to justify PC-to-AS/400 connections are actually pure PC issues-no AS/400 issues are involved at all. Recognize these and remove them from the equation. They may justify a LAN, but they do not warrant a LAN-vs.-emulation debate because access to the AS/400 is no longer the focus-the AS/400 is simply the means to some other end. These issues fall into two broad categories-access to PC software and sharing of DASD and peripherals.
It's tough to validate an intent to share PC-oriented software as a reason to connect all of your PCs to the AS/400. A LAN or file server will allow users to share PC software across many locations. By the same token, any file server can reduce your PC hard disk requirements by acting as a DASD resource. It's not mandatory to involve the AS/400 in any of this, and your midrange system's performance may suffer if you do.
Another common argument I've heard for using a LAN is the sharing of PC printers. This practice is commonplace even though there are other means to address this issue, such as A/B switches. In reality, printer sharing is a thinly veiled version of file sharing. In many cases, the file to be printed at a shared printer is not in the native form that the printer can deal with. It may be an EBCDIC file from an AS/400 which needs to be printed on an ASCII printer. In addition to the printing of the file, the LAN or AS/400 must translate it properly for printing.
Terminal emulators and LANs can both accomplish these tasks. Terminal emulators do it by virtue of "attached" printers or by means of transferring a file from the PC to the AS/400, which in turn routes it through the async controller to an ASCII printer, and so on. LANs handle printer sharing as a matter of course, usually by means of one or more print servers which direct the output from the LAN node to the requested printer.
One of the fastest growing areas in business data communications today, E-mail should be thought of as much more than just message passing. These days, E-mail often includes appointment scheduling, to-do lists, calendars, company bulletin boards and more.
The AS/400's strong suit is not E-mail. I will admit that IBM's solution to E- mail, OfficeVision/400, is a worthy effort. But compared to some of the E-mail products available for LANs, OfficeVision/400 is about two bricks shy of a load.
LAN E-mail offerings are robust, effective and, generally speaking, network- effective. OfficeVision/400 accessed by a terminal emulation card fails on two of the three points just mentioned.
First, OfficeVision/400-actually, all AS/400-based E-mail packages-have a nasty habit of bogging down the AS/400. They are processor hogs. These packages currently are, in my opinion, examples of software better suited to LANs and not well-suited for the AS/400. Secondly, AS/400 E-mail products like Office Vision/400 pale in comparison to the robust nature and built-in flexibility of LAN E-mail packages.
In this arena, terminal emulators take a back seat to LANs. E-mail should not be the deciding factor in the emulator-vs.-LAN question, though. It's important, but does not qualify as a sole reason why a LAN should be installed over a terminal emulator solution. If E-mail is the only "why" in your installation, then take the OfficeVision/400 (or equivalent) route. It seems hard to imagine that the issues of file transfer, resource sharing and common terminal access won't appear in your list of business reasons; but if they don't, and if E-mail is all that's left, skip the LAN.
The Plot Thickens: Costs
It may appear that LANs have really pulled ahead of terminal emulation in this footrace, but don't call your LAN supplier yet! One area where terminal emulators gain ground is cost.
At first glance, it would seem like no one would ever buy a terminal emulator. Terminal emulation boards are routinely available for between $150 and $700, depending on desired features and options. Under normal conditions, the after- purchase terminal emulator costs from year to year are minimal. There really isn't much to spend money on!
While LAN Network Interface Cards (NICs) are comparatively cheaper-depending on the protocol requirements of your LAN, you can obtain a LAN NIC for around $125-keep in mind that a LAN is not just NIC cards. That's the trap-there may be additional startup costs such as an Ethernet or token-ring card for the AS/400, a Multiple Access Unit (MAU) or network management software. In addition, there will always be ongoing support costs associated with a LAN.
A recent survey of Fortune 1000 companies conducted by Forrester Research reveals that the cost to support a LAN user runs around $1,270 per user, per year! LAN administration accounts for 59 percent of that amount; physical LAN support accounts for 22 percent; bridge and router support, 9 percent; Help desk costs, 8 percent; and dial-in support, 2 percent.
Let's Wrap It Up
At this point, it should be clear that a number of issues must be considered before implementing either a terminal emulation solution or a LAN. We've reviewed the basic decision gates such as common terminal access (the race between LANs and terminal emulators is a push), resource sharing (LANs take this one), file transfer (again, LANs by a clear margin) and, finally, E-mail (LANs for the win).
The big issue is cost.
Any LAN is expensive. The hidden costs of supporting the LAN makes a persuasive case for terminal emulators. And if you're wondering by now whether there's a clear-cut answer to which way you should go on this issue (even with costs aside), the answer is no. Every networking and communications issue is fraught with "ifs." But knowing where to start (with the "whys"), what the main criteria for evaluation should be (the four points we discussed) and the costs (both apparent and hidden) should make the process easier for you.
Kris Neely is the connectivity editor at Midrange Computing.