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How to cater for legacy data - (Oct 1999)
In order to enjoy the benefits of server-based computing, you need to make informed decisions about configuration. John Stevenson tells us how to do it.

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Server-based computing promises all the benefits of centralised, host-based computing (security, integrity, scalability, central management), but how do you get access to legacy systems and data?

Statistically, thin-client – or server-based computing to give it its latest marketing label – is small beer. There are many millions of Pentium ‘fat client’ PCs going onto the desks of corporate Britain each year. But every penny-conscious financial director can see the potential in a low-cost desktop, and increasing numbers of IT Managers can see the benefits of a server-based solution that can be managed centrally and won’t have its hard disk wiped by the first errant user to pick up the mouse.

So server-based computing (using Microsoft Terminal Server or Citrix WinFrame/MetaFrame) is on the increase, offering scalable, centralised architectures that are easy and cost-effective to manage. Moving to a server-based computing architecture can be an ideal way of reducing desktop and network management costs, accelerating application deployment (one deployment covers every desktop) or even implementing a rapid Y2K replacement project.

Not as easy as it looks

However, things are rarely this simple and the prospective purchaser must consider a number of issues. The Windows NT servers need to be carefully scaled and sized to ensure they will be up to the host-style tasks they will be asked to perform. The network needs to be examined to ensure it will cope with the type of traffic. Last, and by no means least, is the issue of access to the legacy data and applications (payroll, accounts, order processing, customer records, etc.) that reside on host-based systems elsewhere in the organisation. Typically running on IBM, Unix or Digital platforms, the legacy systems are often green screen applications. They are usually mature, proven, reliable and consulted everyday by a wide range of users across the organisation. So any decision to move to a server-based computing architecture needs an accompanying decision about how the organisation will continue to access its legacy data.

There are a number of host access products on the market, but ideally look for one that is designed specifically for Citrix/Windows Terminal Server environments. The chosen solution should enable you to leverage your existing investments by providing host access to legacy data and applications for virtually any desktop.


Your specific requirements will depend largely on the type of legacy applications and data you need to access but here are a few guidelines:

Easy access.
The user should be able to just click on a predefined icon and the host application should launch immediately. Transparent terminal emulation allows users to access multiple hosts without having to learn complicated host connection procedures.

Breadth of support.
You could well need to support a range of terminal emulation needs and access to several databases. Look for a solution that gives you the widest choice of terminal emulations together with access to all the popular host database formats including Oracle, DB2, Informix, Sybase and Progress. That way users can extract the data they need without having to know which database version or what type of host they are accessing.

Look for a solution that will allow you to customise and leverage existing applications without having to modify host code. Host screens become more user-friendly and assume a GUI look-and-feel by adding Windows, Icons, Mouse Control, Pull Down menus and Scroll Bars.

Integration & management.
Some products offer the capability to restrict certain menu options for particular users. This limits user access to settings and commands to reduce accidental configuration changes that result in help desk calls. A macro language will also allow the administrator to easily record and automate functions such as log-in and file transfer, to hide complexity from users.

Look for a solution that enables you to set up Word and Excel users to access corporate data from their applications. A good product will also include sample source code and applications for Visual Basic, allowing administrators and system integrators to create custom applications for accessing databases and automate remote database tasks with SQL command files.

In summary, some populations of users will be glad to see any new interface that masks the idiosyncrasies of a green screen DB2 database. Others will only be satisfied if the host access product presents exactly the same ‘warts-and-all’ interface they have used for the last 5 years! Moving to a server-based computing environment offers the opportunity to change the way legacy data is displayed and used but you need a high degree of configurability to ensure everyone gets what they want.

John Stevenson was writing on behalf of Esker
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