UNIX Application Migration Guide
Authors: N
Published year: 2003
Pages: 16-18/134

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Migration or Coexistence?

With a large code base of installed UNIX applications, you are probably unlikely to relish the thought of throwing the entire environment out and starting again with an unfamiliar platform. Fortunately, as this guide shows, you do not necessarily have to ” there are methods that will allow you to preserve your investment in UNIX applications while developing under or moving to Windows over a longer period.

This guide deals with the four possible options for migration or coexistence between UNIX and Windows. These are:

Using a quick port.
Completing a full port.
Rewriting the application.
Allowing two versions to coexist.

The following subsections describe these options in greater detail.

Using a Quick Port

One of the simplest migration paths possible is to port the code directly to Microsoft Services for UNIX 3.0. Services for UNIX 3.0 includes Microsoft Interix, which provides a UNIX environment that runs on top of the Windows kernel, allowing your native UNIX applications and scripts to work alongside Windows-based applications.

Completing a Full Port

A full port involves migrating your software to Windows with the minimum changes necessary to allow the application to run. Unlike the quick port, this does entail alterations to the source code, although the number of modifications will depend on the level of standards compliance within the original application.

Rewriting the Application

Rewriting the application is the ideal approach if you want to make full use of all the benefits of migrating to the Windows platform. While initially requiring the greatest amount of work, this course also promises the greatest rewards.

Allowing Versions to Coexist

With coexistence, you retain the original application alongside the new version while simultaneously porting or rewriting the application. Taking this approach significantly reduces risk, because it allows you to use the original system if unexpected issues appear with the new application. However, you will need to employ a cross-platform source code control system to allow concurrent development on both UNIX and Windows simultaneously.

Chapter 3, The Migration Process, and Chapter 4, Assessment and Analysis, cover these options in greater detail, allowing you to decide which is the most appropriate choice or combination of choices for your particular environment.

Summary

In this chapter, you looked at the main factors behind considering a move from your current UNIX environment and the twin options of migrating to Linux or to Windows. You reviewed the advantages and disadvantages of each approach and the issues that migration to Linux entails. You were introduced to the four migration and coexistence paths and covered the benefits of Windows 2000 as an operating environment.

At this point, you should have some understanding of the concepts behind UNIX-to-Windows migration, which are discussed in greater detail throughout this guide. Now it s time to move on to reviewing the backgrounds to both Windows and UNIX and their similarities and differences.

Chapter 2: Windows and UNIX Compared

Introduction

The UNIX Application Migration Guide was developed to help you migrate UNIX applications to the Microsoft Windows operating system. This guide provides the information you need to plan and budget your migration. It also examines methods for carrying out the migration, and provides guidelines on implementing and managing the final product.

By migrating your application to the Windows platform, you benefit from a widely used, full-featured operating system that runs the most popular business applications. With the addition of native UNIX packages such as Microsoft Interix, Windows can run many UNIX applications with a minimum of migration effort. The combination of the Windows platform and the Interix subsystem provides customers with a single enterprise platform on which they can run all of their Windows-based, UNIX, and Internet applications.

This guide is appropriate for managers, architects , and developers involved in the process of migrating an application from UNIX to Windows. Individual chapters cover the different aspects of the migration ” including analysis, planning, porting of code, and testing of the migrated application.

This chapter gives an overview of the development and production environments in both Windows and UNIX. However, before you begin to plan your migration, it is important that you have a good understanding of both operating systems, their terminology, and the key differences between them.

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