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Software Engineering (CS453)
Mr. Naveed Ashraf email id: naveed@biit.edu.pk, Whatsapp# 0345-5001017
Ms. Maryam email id: Maryam@biit.edu.pk, Whatsapp#
(Week 8) Lecture 27-28
Chapter 13: “System Implementation”
Objectives:
After studying this chapter, you should be able to:
Overview of the system implementation process.
Describe how software applications are tested.
Apply four installation strategies: direct, parallel, single-location, and
phased installation.
List the deliverables for documenting the system and for training and
supporting users
Explain why system implementation sometimes fails.
Describe the threats to system security and remedies that can be applied.
InstallatIon:
The process of moving from the current information system to the new one is
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Software Engineering (CS453)
Mr. Naveed Ashraf email id: naveed@biit.edu.pk, Whatsapp# 0345-5001017
Ms. Maryam email id: Maryam@biit.edu.pk, Whatsapp#
called installation.
The organizational process of changing over from the current information system to a
new one.
All employees who use a system, whether they were consulted during the development
process or not, must give up their reliance on the current system and begin to rely on
the new system
Four different approaches to installation have emerged over the years: direct, parallel,
single-location, and phased
The approach an organization decides to use will depend on the scope and complexity
of the change associated with the new system and the organization’s risk aversion.
Direct Installation:
Changing over from the old information system to a new one by turning off the old
system when the new one is turned on.
The direct, or abrupt, approach to installation (also called “cold turkey”) is as sudden as
the name indicates: The old system is turned off and the new system is turned on
Under direct installation, users are at the mercy of the new system. Any errors resulting
from the new system will have a direct impact on the users and how they do their jobs
In some casesdepending on the centrality of the system to the organizationon how
the organization performs
its business.
If the new system fails, considerable delay may occur until the old system can again be
made operational and business transactions are reentered to make the database up to
date.
Direct installation can be very risky.
Direct installation requires a complete installation of the whole system
it is the least expensive installation method
Direct Installation
Parallel Installation:
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Software Engineering (CS453)
Mr. Naveed Ashraf email id: naveed@biit.edu.pk, Whatsapp# 0345-5001017
Ms. Maryam email id: Maryam@biit.edu.pk, Whatsapp#
Running the old information system and the new one at the same time until
management decides the old system can be turned off.
Parallel installation is as riskless as direct installation is risky.
Under parallel installation, the old system continues to run alongside the new system
until users and management
All of the work done by the old system is concurrently performed by the new system.
Outputs are compared (to the greatest extent possible) to help determine whether the
new system is performing as well as the old
Errors discovered in the new system do not cost the organization much, if anything,
because errors can be isolated and the business can be supported with the old system
Because all work is essentially done twice, a parallel installation can be very expensive
Running two systems implies employing (and paying) two staffs to not only operate both
systems, but also to maintain them.
A parallel approach can also be confusing to users because they must deal with both
systems
A parallel approach may not be feasible, especially if the users of the system (such as
customers) cannot tolerate redundant effort or if the size of the system (number of
users or extent of features) is large
Parallel Installation
Single-location Installation
Single-location installation, also known as location or pilot installation, is a middle of-
the-road approach compared with direct and parallel installation
Trying out a new information system at one site and using the experience to decide if
and how the new system should be deployed throughout the organization
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Software Engineering (CS453)
Mr. Naveed Ashraf email id: naveed@biit.edu.pk, Whatsapp# 0345-5001017
Ms. Maryam email id: Maryam@biit.edu.pk, Whatsapp#
Rather than convert all of the organization at once, single-location installation involves
changing from the current to the new system in only one place or in a series of separate
sites over time.
The single location may be a branch office, a single factory, or one department, and the
actual approach used for installation in that location may be any of the other
approaches
The key advantage to single-location installation is that it limits potential damage and
potential cost by limiting the effects to a single site.
Once management has determined that installation has been successful at one location,
the new system may be deployed in the rest of the organization, possibly continuing
with installation at one location at a time
Problems with the system (the actual software as well as documentation, training, and
support) can be resolved before deployment to other sites.
Single-location installation (with direct installation at each location)
Phased Installation:
Phased installation, also called staged installation, is an incremental approach.
Changing from the old information system to the new one incrementally, starting with
one or a few functional components and then gradually extending the installation to
cover the whole new system.
With phased installation, the new system is brought online in functional components;
different parts of the old and new systems are used in cooperation until the whole new
system is installed
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