Legacy System Essay

2583 Words 11 Pages
Legacy Systems


Older software systems that remain vital to an organisation ©Ian Sommerville Software Engineering, 6th edition. Chapter 26

Slide 1

Objectives







To explain what is meant by a legacy system and why these systems are important
To introduce common legacy system structures To briefly describe function-oriented design
To explain how the value of legacy systems can be assessed

©Ian Sommerville Software Engineering, 6th edition. Chapter 26

Slide 2

Topics covered




Legacy system structures
Legacy system design
Legacy system assessment

©Ian Sommerville Software Engineering, 6th edition. Chapter 26

Slide 3

Legacy systems
Software systems that are developed
…show more content…
Chapter 26

Slide 6

The legacy dilemma





It is expensive and risky to replace the legacy system
It is expensive to maintain the legacy system
Businesses must weigh up the costs and risks and may choose to extend the system lifetime using techniques such as reengineering.

©Ian Sommerville Software Engineering, 6th edition. Chapter 26

Slide 7

Legacy system structures


Legacy systems can be considered to be socio-technical systems and not simply software systems









System hardware - may be mainframe hardware
Support software - operating systems and utilities
Application software - several different programs
Application data - data used by these programs that is often critical business information
Business processes - the processes that support a business objective and which rely on the legacy software and hardware
Business policies and rules - constraints on business operations ©Ian Sommerville Software Engineering, 6th edition. Chapter 26

Slide 8

Legacy system components
Support
software

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