C
HAPTER 20
Systems Design,
Implementation, and
Operation
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INTRODUCTION
• Questions to be addressed in this chapter
include:
– What are the activities that take place in the
conceptual design phase of the systems development
life cycle (SDLC)?
– What activities take place in the physical systems
design phase?
– What happens during the systems implementation
and conversion process?
– What activities occur in the systems operation and
maintenance process?
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INTRODUCTION
• Accountants must understand the entire systems
development process, because they are
involved in several ways:
– Helping to specify their needs.
– As members of the development team.
– As auditors after the fact.
• Accountants also help keep the project on track
by:
– Evaluating and measuring benefits.
– Measuring costs.
– Ensuring the project stays on schedule.
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INTRODUCTION
• Effective systems analysis and design
can ensure that developers:
– Correctly define the business problem.
– Design the appropriate solution.
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INTRODUCTION
• The crucial phases of the SDLC include:
– Systems analysis to define the new systems
requirements (discussed in Chapter 18).
– The phases discussed in this chapter, which
include:
•
•
•
•
Conceptual systems design
Physical systems design
Systems implementation and conversion
Operation and maintenance
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Accounting Information Systems, 11/e
Romney/Steinbart
5 of 173
INTRODUCTION
• The crucial phases of the SDLC include:
– Systems analysis to define the new systems
requirements (discussed in Chapter 18).
– The phases discussed in this chapter, which
include:
•
•
•
•
Conceptual systems design
Physical systems design
Systems implementation and conversion
Operation and maintenance
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6 of 173
CONCEPTUAL SYSTEMS DESIGN
• In the conceptual systems design
phase, a general framework is created for
implementing user requirements and
solving the problems identified in the
analysis phase.
• The three main steps are:
– Evaluate design alternatives.
– Prepare design specifications.
– Prepare the conceptual systems design
report.
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Conceptual
Systems
Design
Evaluate
Design
Alternatives
Systems
Analysis
Prepare
Design
Specifications
Prepare
Conceptual Systems
Design Report
Physical
Design
Implementation
and
Conversion
Operation
and
Maintenance
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8 of 173
Systems
Analysis
Evaluate
Design
Alternatives
Prepare
Design
Specifications
Prepare
Conceptual Systems
Design Report
Physical
Design
Implementation
and
Conversion
Operation
and
Maintenance
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CONCEPTUAL SYSTEMS DESIGN
• Evaluating design alternatives
– There are many design decisions that must
be made. For example:
• Should a document be hard-copy or sent by EDI?
• Should the company use a large centralized
mainframe or some form of distributed processing?
• What form should data entry take, e.g., keyboard,
optical character recognition, POS devices?
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CONCEPTUAL SYSTEMS DESIGN
• Also, there are many ways to approach the
systems development process:
–
–
–
–
Packaged software
In-house development
End-user development
Outsourcing
• The company also chooses between:
– Modifying or enhancing existing software
– Replacing existing software
– Reengineering its business processes
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CONCEPTUAL SYSTEMS DESIGN
• The design team should identify a variety of
design alternatives and evaluate each with
respect to:
– How well it meets organizational and system
objectives
– How well it meets user needs
– Whether it is economically feasible
– Its advantages and disadvantages
• The steering committee evaluates the
alternatives.
• Click here to view some of the design
considerations and alternatives from Table 20-1
in your textbook.
Design Considerations
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Systems
Analysis
Evaluate
Design
Alternatives
Prepare
Design
Specifications
Prepare
Conceptual Systems
Design Report
Physical
Design
Implementation
and
Conversion
Operation
and
Maintenance
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CONCEPTUAL SYSTEMS DESIGN
• Prepare design specifications
– Once a design has been selected, the
project team develops the conceptual
design specifications for the following
elements:
• Output
• Because output is what goes to the user and the
system must be designed to meet user needs, the
output specifications are prepared first.
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CONCEPTUAL SYSTEMS DESIGN
• Prepare design specifications
– Once a design has been selected, the
project team develops the conceptual
design specifications for the following
elements:
• Output
• Data storage
• How will data be stored to produce the desired
outputs?
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CONCEPTUAL SYSTEMS DESIGN
• Prepare design specifications
– Once a design has been selected, the
project team develops the conceptual
design specifications for the following
elements:
• Output
• Data storage
• Input
• What types of data must be entered to produce the
desired outputs?
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CONCEPTUAL SYSTEMS DESIGN
• Prepare design specifications
– Once a design has been selected, the
project team develops the conceptual
design specifications for the following
elements:
• Output
• Data
storage
• How will data be processed and in what sequence
• Inputto produce the desired outputs?
• Processing procedures and operations
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Systems
Analysis
Evaluate
Design
Alternatives
Prepare
Design
Specifications
Prepare
Conceptual Systems
Design Report
Physical
Design
Implementation
and
Conversion
Operation
and
Maintenance
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CONCEPTUAL SYSTEMS DESIGN
• Prepare the conceptual systems design
report
– A conceptual systems design report is
prepared at the end of the conceptual design
phase to:
• Guide physical system design activities.
• Communicate how management and user
information needs will be met.
• Help the steering committee assess system
feasibility.
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CONCEPTUAL SYSTEMS DESIGN
• The main component is a description of one or
more recommended system designs. This
description contains:
– The contents of each output, database, and input.
– Processing flows and the relationships among
programs, files, inputs, and outputs.
– Hardware, software, and resource requirements.
– Audit, control, and security processes and
procedures.
– A discussion of assumptions or unresolved problems
that might affect the final design.
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INTRODUCTION
• The crucial phases of the SDLC include:
– Systems analysis to define the new systems
requirements (discussed in Chapter 18).
– The phases discussed in this chapter, which
include:
•
•
•
•
Conceptual systems design
Physical systems design
Systems implementation and conversion
Operation and maintenance
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PHYSICAL SYSTEMS DESIGN
• During the physical systems design phase, the
company determines how the conceptual AIS
design is to be implemented.
– The broad, user-oriented requirements of conceptual
design are translated into detailed specifications used
to code and test computer programs.
– Phases include:
•
•
•
•
•
•
Designing output
Creating files and databases
Designing input
Writing computer programs
Developing procedures
Building in controls
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Systems
Analysis
Physical
Systems
Design
Output
Design
Conceptual
Systems
Design
File and DB
Design
Input
Design
Program
Design
Procedures
Design
Controls
Design
Implementation
and
Conversion
Operation
and
Maintenance
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Systems
Analysis
Conceptual
Systems
Design
Output
Design
File and DB
Design
Input
Design
Program
Design
Procedures
Design
Controls
Design
Implementation
and
Conversion
Operation
and
Maintenance
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PHYSICAL SYSTEMS DESIGN
• Output design
– The objective of output design is to
determine the nature, format, content,
and timing of printed reports,
documents, and screen displays.
• Requires cooperation between users and
designers.
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PHYSICAL SYSTEMS DESIGN
• Important design considerations include:
– Use of the output
• Who will use it and why?
• When is it needed?
• What decisions will it facilitate?
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PHYSICAL SYSTEMS DESIGN
• Important design considerations include:
– Use of the output
– Output medium
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•
•
•
•
•
•
Paper
Screen
Voice response
Diskette
Microfilm
Other
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PHYSICAL SYSTEMS DESIGN
• Important design considerations include:
– Use of the output
– Output medium
– Output format •
Should select the format that
clearly conveys the most
information.
• Could be:
– Table
– Narrative
– Graphic
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PHYSICAL SYSTEMS DESIGN
• Important design considerations include:
– Use of the output
– Output medium
– Output format
– Pre-printed • Should paper output be on
preprinted form and/or
turnaround document?
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PHYSICAL SYSTEMS DESIGN
• Important design considerations include:
– Use of the output
– Output medium
– Output format
– Pre-printed
– Location • Where is the output to be
sent?
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PHYSICAL SYSTEMS DESIGN
• Important design considerations include:
– Use of the output
– Output medium
– Output format
– Pre-printed
– Location
– Access • Who should be able to
access hard-copy and
screen output?
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PHYSICAL SYSTEMS DESIGN
• Important design considerations include:
– Use of the output
– Output medium
– Output format
– Pre-printed
– Location • Lengthy output should be preceded by an
executive summary and a table of contents.
– Access
• Headings and legends organize data and
– Detail
highlight important items.
• Detailed info goes in an appendix.
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PHYSICAL SYSTEMS DESIGN
• Important design considerations include:
– Use of the output
– Output medium
– Output format
– Pre-printed
– Location
– Access
– Detail • How often should the output be produced?
– Timeliness
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PHYSICAL SYSTEMS DESIGN
• Outputs usually fit into one of the following
four categories:
– Scheduled reports
• Have pre-specified content and format.
• Are prepared on a regular basis.
• Examples:
– Weekly sales analysis
– Monthly financial statements
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PHYSICAL SYSTEMS DESIGN
• Outputs usually fit into one of the following
four categories:
– Scheduled reports
– Special-purpose analysis reports
• No pre-specified content and format.
• Typically prepared in response to a
management request.
• Example:
– Analysis of impact of a government
mandate on profitability
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PHYSICAL SYSTEMS DESIGN
• Outputs usually fit into one of the following
four categories:
– Scheduled reports
– Special-purpose analysis reports
– Triggered exception reports
• Have pre-specified content and format.
• Prepared only in response to abnormal
conditions, i.e., the “trigger.”
• Example:
– Cost overruns
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PHYSICAL SYSTEMS DESIGN
• Outputs usually fit into one of the following
four categories:
– Scheduled reports
– Special-purpose analysis reports
– Triggered exception reports
– Demand reports
• Have pre-specified content and format.
• Prepared only on request.
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PHYSICAL SYSTEMS DESIGN
• AIS developers prepare sample outputs
and users evaluate them to ensure they
are complete, relevant, and useful.
– Modifications are made as needed to ensure
acceptability.
– Many organizations require users to sign off
on these documents before proceeding
through the SDLC.
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Systems
Analysis
Conceptual
Systems
Design
Output
Design
File and DB
Design
Input
Design
Program
Design
Procedures
Design
Controls
Design
Implementation
and
Conversion
Operation
and
Maintenance
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PHYSICAL SYSTEMS DESIGN
• File and database design
– Various company segments need to store data in
compatible formats so that data can be shared across
units.
– Important file and database design considerations
include:
• Hard drive
• Storage medium
© 2008 Prentice Hall Business Publishing
•
•
•
•
•
Disk
Diskette
CD
Tape
Paper
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PHYSICAL SYSTEMS DESIGN
• File and database design
– Various company segments need to store data in
compatible formats so that data can be shared across
units.
– Important file and database design considerations
include:
• Storage medium
• Processing mode
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• Manual
• Batch
• Real time
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PHYSICAL SYSTEMS DESIGN
• File and database design
– Various company segments need to store data in
compatible formats so that data can be shared across
units.
– Important file and database design considerations
include:
• Storage medium
• Processing mode
• Maintenance • What procedures are needed to
effectively maintain the data?
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PHYSICAL SYSTEMS DESIGN
• File and database design
– Various company segments need to store data in
compatible formats so that data can be shared across
units.
– Important file and database design considerations
include:
•
•
•
•
Storage medium
Processing mode
Maintenance
Size • How many records and how big are they?
• How fast are they expected to grow?
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PHYSICAL SYSTEMS DESIGN
• File and database design
– Various company segments need to store data in
compatible formats so that data can be shared across
units.
– Important file and database design considerations
include:
•
•
•
•
•
Storage medium
• What portion of records are added or
Processing mode
deleted each year?
Maintenance
• What portion needs to be updated?
Size
Activity level
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Systems
Analysis
Conceptual
Systems
Design
Output
Design
File and DB
Design
Input
Design
Program
Design
Procedures
Design
Controls
Design
Implementation
and
Conversion
Operation
and
Maintenance
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PHYSICAL SYSTEMS DESIGN
• Input design
– Systems designers must identify the
different types of data input and optimal
input methods.
– There are two principal types of data
input:
• Forms
• Computer screens
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PHYSICAL SYSTEMS DESIGN
• Considerations in input design include:
– Input medium
© 2008 Prentice Hall Business Publishing
•
•
•
•
•
•
Keyboard
OCR
MICR
POS terminal
EDI
Voice input
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PHYSICAL SYSTEMS DESIGN
• Considerations in input design include:
– Input medium
– Input source
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• Where do data originate?
– Computer
– Customer
– Remote location
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PHYSICAL SYSTEMS DESIGN
• Considerations in input design include:
– Input medium
– Input source
– Input format • What format captures the data with
the least effort or cost?
– Source or turnaround document
– Screen
– Source data automation
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PHYSICAL SYSTEMS DESIGN
• Considerations in input design include:
–
–
–
–
Input medium
Input source
Input format
Input type • What is the nature of the data?
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PHYSICAL SYSTEMS DESIGN
• Considerations in input design include:
–
–
–
–
–
Input medium
Input source
Input format
Input type
Volume • How much data are to be entered?
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PHYSICAL SYSTEMS DESIGN
• Considerations in input design include:
–
–
–
–
–
–
Input medium
Input source
Input format
Input type
Volume
Personnel
• What functions and expertise do the data
entry operators have?
• Is additional training necessary?
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PHYSICAL SYSTEMS DESIGN
• Considerations in input design include:
–
–
–
–
–
–
–
Input medium
Input source
Input format
Input type
Volume
Personnel
• How often is data to be entered?
Frequency
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PHYSICAL SYSTEMS DESIGN
• Considerations in input design include:
–
–
–
–
–
–
–
–
Input medium
Input source
Input format
Input type
Volume
Personnel
Frequency  How can costs be minimized without
adversely affecting efficiency and
Cost
accuracy?
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PHYSICAL SYSTEMS DESIGN
• Considerations in input design include:
–
–
–
–
–
–
–
–
–
Input medium
Input source
Input format
Input type
Volume
Personnel
Frequency • What errors are possible?
• How can they be detected and corrected?
Cost
Error detection and correction
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• Preprint as muchSYSTEMS
data as possible. DESIGN
PHYSICAL
• Use appropriate weight and grade of paper.
• Use bold type, double-thick lines, and shading to
highlight different parts of the form.
• Use a standard size and one that is consistent with
Although
inputforisfiling,
evolving
toward
source data
requirements
binding,
or mailing.
• If mailed to external
parties, position
address for
automation,
forms design
is still the
important.
placement in a window envelope.
Following
are important principles for
• Have copies of the form printed in different colors to
designing
new forms
and evaluating existing
facilitate accurate
distribution.
• Include clear instructions for completing the form.
ones:
• Forms design
–
–
• General considerations
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PHYSICAL SYSTEMS DESIGN
• Forms design
– Although input is evolving toward source data
automation, forms design is still important.
• Place the form name at the top in bold type.
– Following are
important
principles
for
• Have
the forms
pre-numbered
designing newconsecutively.
forms and evaluating existing
• If distributed to external parties, have
ones:
company name and address pre-printed on
• General considerations
the form.
• Introductory section of form
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PHYSICAL SYSTEMS DESIGN
• Forms design
–
–
• Group together logically related information
Although input(e.g.,
is evolving
toward
source
data
info about the
customer,
info about
the product).
automation, forms
design is still important.
• Provide sufficient room to record each item.
Following are important principles for
• Order the data items consistent with the
designing newsequence
forms in
and
evaluating
existing
which
the data is likely
to be
gathered.
ones:
• Use codes and check-offs in places where
• General considerations
standardized explanations are likely.
• Introductory section of form
• Main body of form
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PHYSICAL SYSTEMS DESIGN
• Forms Design
– Although input is evolving toward source data
automation, forms design is still important.
• Provide
space
for:
– Following are
important
principles
for
– Recording final disposition of the form.
designing new
forms and evaluating existing
– Approval signatures.
ones:
– Dates of approval and final disposition.
•
•
•
•
General considerations
– A dollar or numeric total.
Introductory
sectionindicate
of form the distribution of
• Clearly
each
Main body of
formform.
Conclusion section of form
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PHYSICAL SYSTEMS DESIGN
• Designing computer screens
– It is more efficient to enter data directly into
the computer than to record it on paper for
subsequent entry.
– Therefore, it’s important to design computer
screens for input as well as output.
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PHYSICAL SYSTEMS DESIGN
• Computer screens are most effective when the following
principles are used:
– Organize the screen for quick, accurate, and complete entry
of the data.
• Minimize input by retrieving as much as possible from
the system.
• Example: If the customer number is entered, retrieve his
name/address data from the system.
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PHYSICAL SYSTEMS DESIGN
• Computer screens are most effective when the following
principles are used:
– Organize the screen for quick, accurate, and complete entry of
the data.
– Enter data in the same order it appears on the document.
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PHYSICAL SYSTEMS DESIGN
• Computer screens are most effective when the following
principles are used:
– Organize the screen for quick, accurate, and complete entry of
the data.
– Enter data in the same order it appears on the document.
– Complete the screen from left to right and top to bottom,
grouping logically related data together.
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PHYSICAL SYSTEMS DESIGN
• Computer screens are most effective when the following
principles are used:
– Organize the screen for quick, accurate, and complete entry of
the data.
– Enter data in the same order it appears on the document.
– Complete the screen from left to right and top to bottom,
grouping logically related data together.
– Design the screen so users can jump from one data entry
location to another or use a single key to go directly to
screen locations.
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PHYSICAL SYSTEMS DESIGN
• Computer screens are most effective when the following
principles are used:
– Organize the screen for quick, accurate, and complete entry of
the data.
– Enter data in the same order it appears on the document.
– Complete the screen from left to right and top to bottom,
grouping logically related data together.
– Design the screen so users can jump from one data entry
location to another or use a single key to go directly to screen
locations.
– Make it easy to correct mistakes.
• Use clear and explicit error messages that are consistent
on all screens.
• Provide a help feature for online assistance.
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PHYSICAL SYSTEMS DESIGN
• Computer screens are most effective when the following
principles are used:
– Organize the screen for quick, accurate, and complete entry of
the data.
– Enter data in the same order it appears on the document.
– Complete the screen from left to right and top to bottom,
grouping logically related data together.
– Design the screen so users can jump from one data entry
location to another or use a single key to go directly to screen
locations.
• Limit the number of menu options on a single screen.
– Make it easy to correct mistakes.
– Avoid clutter by restricting the amount of data on one
screen.
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Systems
Analysis
Conceptual
Systems
Design
Output
Design
File and DB
Design
Input
Design
Program
Design
Procedures
Design
Controls
Design
Implementation
and
Conversion
Operation
and
Maintenance
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PHYSICAL SYSTEMS DESIGN
• Program design
– Program development is one of the most timeconsuming activities in the SDLC.
– A structured programming process should be
followed:
• With structured programming, programs should be
subdivided into small, well-defined modules to reduce
complexity and enhance reliability and modifiability.
• Modules should interact with a control module rather than
with each other.
• To facilitate testing and modification, each module should
have only one entry and exit point.
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PHYSICAL SYSTEMS DESIGN
• To improve software quality, organizations
should develop programming standards (rules
for writing programs).
– Contributes to consistency among programs.
– Makes them easier to read and maintain.
• Consider doing structured program walkthroughs to find incorrect logic, errors,
omissions, or other problems.
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PHYSICAL SYSTEMS DESIGN
• Program preparation time may range from a few
days to a few years, depending on complexity.
• Though accountants need not be programmers,
they should understand how software is created.
• The following slides discuss the eight steps for
developing software and where these steps take
place in the SDLC.
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PHYSICAL SYSTEMS DESIGN
Systems
Analysis
• STEP ONE: Determine user
needs.
Conceptual
Design
– Occurs during the systems analysis
stage of the SDLC.
Physical
Design
Implementation
and
Conversion
Operation
and
Maintenance
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PHYSICAL SYSTEMS DESIGN
Systems
Analysis
• STEP TWO: Develop and
document a plan.
Conceptual
Design
– Occurs during the conceptual design
phase and the beginning of physical
design.
Physical
Design
Implementation
and
Conversion
Operation
and
Maintenance
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PHYSICAL SYSTEMS DESIGN
Systems
Analysis
• STEP THREE: Write the program
code.
Conceptual
Design
Physical
Design
Implementation
and
Conversion
– Design in increasing levels of detail,
known as hierarchical program
design.
– Begun during systems design and
completed during systems
implementation.
Operation
and
Maintenance
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PHYSICAL SYSTEMS DESIGN
Systems
Analysis
Conceptual
Design
Physical
Design
Implementation
and
Conversion
Operation
and
Maintenance
• STEP FOUR: Test the program code.
– Debugging is discovering and
eliminating program errors.
– Desk checking happens after a
program is coded and involves a
visual and mental review to discover
programming errors.
– Programs are tested for logic errors
using test data that simulates both
valid transactions and all possible
error conditions.
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PHYSICAL SYSTEMS DESIGN
Systems
Analysis
Conceptual
Design
Physical
Design
Implementation
and
Conversion
– Large programs are often tested
in three stages:
• Individual program modules.
• The linkages between the module
and the control module.
• The interfaces between the
program being tested and other
application programs.
Operation
and
Maintenance
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PHYSICAL SYSTEMS DESIGN
Systems
Analysis
Conceptual
Design
Physical
Design
– Errors need to be found as soon
as possible in the development
process.
– Errors discovered late cost 80–
1000% more to fix than those
found early.
Implementation
and
Conversion
Operation
and
Maintenance
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PHYSICAL SYSTEMS DESIGN
Systems
Analysis
Conceptual
Design
Physical
Design
Implementation
and
Conversion
Operation
and
Maintenance
• STEP FIVE: Document the
program.
– Documentation explains how
programs work and helps
correct and resolve errors.
– Includes flowcharts, record
layouts, E-R diagrams, REA
data models, narrative
descriptions of the system, etc.,
organized in a manual.
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PHYSICAL SYSTEMS DESIGN
Systems
Analysis
Conceptual
Design
• STEP SIX: Train program users.
– Often uses the program
documentation.
Physical
Design
Implementation
and
Conversion
Operation
and
Maintenance
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PHYSICAL SYSTEMS DESIGN
Systems
Analysis
Conceptual
Design
• STEP SEVEN: Install the system.
- All components are brought
together, and the company
begins to use the system.
Physical
Design
Implementation
and
Conversion
Operation
and
Maintenance
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PHYSICAL SYSTEMS DESIGN
Systems
Analysis
• STEP EIGHT: Use and modify
the system.
Conceptual
Design
Physical
Design
Implementation
and
Conversion
Operation
and
Maintenance
© 2008 Prentice Hall Business Publishing
– Program maintenance is a
response to any factors that
require program revision.
– Includes requests for:
• New or revised reports.
• Changes in input, file content, or
values such as tax rates.
• Error detection and correction.
• Conversion to new hardware.
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Systems
Analysis
Conceptual
Systems
Design
Output
Design
File and DB
Design
Input
Design
Program
Design
Procedures
Design
Controls
Design
Implementation
and
Conversion
Operation
and
Maintenance
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PHYSICAL SYSTEMS DESIGN
• Procedures design
– Individuals who interact with a newlydesigned AIS need procedures to cover:
•
•
•
•
•
•
•
•
Input preparation
Transaction processing
Error detection and correction
Controls
Reconciliation of balances
Database access
Output preparation and distribution
Computer operator instructions
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PHYSICAL SYSTEMS DESIGN
• Procedures may take the form of:
– System manuals
– User instruction classes
– Training materials
– Online help screens
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PHYSICAL SYSTEMS DESIGN
• The procedures may be written by:
– Development teams;
– Users; or
– Teams representing both groups.
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Systems
Analysis
Conceptual
Systems
Design
Output
Design
File and DB
Design
Input
Design
Program
Design
Procedures
Design
Controls
Design
Implementation
and
Conversion
Operation
and
Maintenance
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PHYSICAL SYSTEMS DESIGN
• Controls design
– Improperly controlled input, processing, and
database functions produce information of
questionable value.
– Controls must be built into an AIS to ensure its
effectiveness, efficiency, and accuracy. These
controls should:
• Minimize errors.
• Detect and correct errors when they do occur.
– Accountants play a vital role in this area.
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PHYSICAL SYSTEMS DESIGN
• Important control concerns that must be
addressed include:
– Validity
• Are all interactions valid?
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PHYSICAL SYSTEMS DESIGN
• Important control concerns that must be
addressed include:
– Validity
– Authorization
• Are input, processing, storage, and
output activities authorized by the
appropriate managers?
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PHYSICAL SYSTEMS DESIGN
• Important control concerns that must be
addressed include:
– Validity
– Authorization
– Accuracy • Is input verified to ensure accuracy?
• What controls ensure that data is not
lost when passing between processing
activities?
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PHYSICAL SYSTEMS DESIGN
• Important control concerns that must be
addressed include:
–
–
–
–
Validity
Authorization
Accuracy
Security
• Is the system protected against:
– Unauthorized physical and logical access to prevent
improper use, alteration, destruction, or disclosure of
information and software?
– Theft of system resources?
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PHYSICAL SYSTEMS DESIGN
• Important control concerns that must be
addressed include:
–
–
–
–
–
Validity
Authorization
Accuracy
Security
Numerical control
• Are documents pre-numbered to prevent errors or
intentional misuse and to detect when documents are
missing or stolen?
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PHYSICAL SYSTEMS DESIGN
• Important control concerns that must be
addressed include:
–
–
–
–
–
–
Validity
Authorization
Accuracy
Security
Numerical control
Availability
• Is the system available as set forth in agreements?
• Can users enter, update, and retrieve data during those
times?
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PHYSICAL SYSTEMS DESIGN
• Important control concerns that must be
addressed include:
–
–
–
–
–
–
–
Validity
• Can the system be modified without affecting system
Authorization
availability, security, and integrity?
Accuracy
• Are only authorized, tested, and documented changes
made to the system and data?
Security
• Are resources available to manage, schedule, document,
Numerical
control
and communicate changes to management and
authorized users?
Availability
Maintainability
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PHYSICAL SYSTEMS DESIGN
• Important control concerns that must be
addressed include:
–
–
–
–
–
–
–
–
Validity
Authorization
Accuracy
Security
Is processing complete, accurate, timely, and
Numerical• control
authorized?
Availability• Is it free from unauthorized or inadvertent
manipulations?
Maintainability
Integrity
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PHYSICAL SYSTEMS DESIGN
• Important control concerns that must be
addressed include:
–
–
–
–
–
–
–
–
–
Validity
Authorization
Accuracy
Security
Numerical control
Availability
• Can data be traced from source to output and vice
Maintainability
versa?
Integrity
Audit trail
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PHYSICAL SYSTEMS DESIGN
• Physical systems design report
– At the end of the physical design phase, a
physical systems design report is
prepared, summarizing what was
accomplished.
– This report serves as the basis for
management’s decision whether to proceed to
implementation.
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INTRODUCTION
• The crucial phases of the SDLC include:
– Systems analysis to define the new systems
requirements (discussed in Chapter 18).
– The phases discussed in this chapter, which
include:
•
•
•
•
Conceptual systems design
Physical systems design
Systems implementation and conversion
Operation and maintenance
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SYSTEMS IMPLEMENTATION AND
CONVERSION
• Systems implementation
– Systems implementation is the process of
installing hardware and software and
getting the AIS up and running.
– Phases include:
•
•
•
•
•
•
Developing a plan
Preparing the site
Installing and testing hardware and software
Selecting and training personnel
Completing documentation
Testing the system
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Systems
Analysis
Conceptual
Systems
Design
System
Implementation
and
Conversion
Implementation
Planning
Physical
Systems
Design
Prepare Site;
Install and Test
Hardware
Complete
Documentation
Conversion
Select and Train
Personnel
Test
System
Operation
and
Maintenance
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Systems
Analysis
Conceptual
Systems
Design
Physical
Systems
Design
Implementation
Planning
Prepare Site;
Install and Test
Hardware
Complete
Documentation
Conversion
Select and Train
Personnel
Test
System
Operation
and
Maintenance
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SYSTEMS IMPLEMENTATION AND
CONVERSION
• Implementation planning
– An implementation plan consists of:
•
•
•
•
Implementation tasks
Expected completion dates
Cost estimates
Specification of the person(s) responsible for each task
– The plan specifies when the project should be
complete and operational.
– The implementation team should identify risk
factors that decrease the likelihood of successful
implementation, and the plan should contain a
strategy for coping with each of the risks.
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SYSTEMS IMPLEMENTATION AND
CONVERSION
• AIS changes may require adjustments to the
company’s organizational structure,
including:
– Creation of new departments.
– Elimination or downsizing of existing
departments.
– Changes even in the data processing department.
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Systems
Analysis
Conceptual
Systems
Design
Physical
Systems
Design
Implementation
Planning
Prepare site;
Install and Test
hardware
Complete
Documentation
Conversion
Select and Train
Personnel
Test
System
Operation
and
Maintenance
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SYSTEMS IMPLEMENTATION AND
CONVERSION
• Site preparation
– A large computer may require changes such as:
• New electrical outlets
• Data communications facilities
• Raised floors
• Humidity controls
• Special lighting
• Air-conditioning
• Security measures, such as:
– Fire protection
– Emergency power supply
• Space for equipment, storage, and offices
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SYSTEMS IMPLEMENTATION AND
CONVERSION
 Site preparation is a lengthy process and
should begin well ahead of the installation
date.
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Systems
Analysis
Conceptual
Systems
Design
Physical
Systems
Design
Implementation
Planning
Prepare Site;
Install and Test
Hardware
Complete
Documentation
Conversion
Select and Train
Personnel
Test
System
Operation
and
Maintenance
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SYSTEMS IMPLEMENTATION AND
CONVERSION
• Select and train personnel
– Employees can be hired from outside or
transferred internally.
• Hiring from within is usually more effective and
less costly, because the employees already
understand the business.
• Transferring displaced employees can enhance
loyalty and morale.
– Companies take training shortcuts because:
• Effective training is time-consuming and
expensive.
• Those who understand the system are maintaining
and upgrading it.
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SYSTEMS IMPLEMENTATION AND
CONVERSION
• When training is insufficient, the company will
not achieve the expected return on investment.
• The hidden cost is that users will turn to their
coworkers who have mastered the system for
help. Results in:
– Less productive coworkers
– Increased costs
• Effective training includes:
– Hardware and software skills
– Orientation to new policies and operations
• The training should be scheduled just before
systems testing and conversion.
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SYSTEMS IMPLEMENTATION AND
CONVERSION
• Types of training include:
– Technical training from vendors
– Self-study manuals
– Computer-aided instruction
– Videotape presentations
– Role-playing
– Case studies
– Experimenting with the AIS under the
guidance of experienced users
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Systems
Analysis
Conceptual
Systems
Design
Physical
Systems
Design
Implementation
Planning
Prepare site;
Install and Test
Hardware
Complete
Documentation
Conversion
Select and Train
Personnel
Test
System
Operation
and
Maintenance
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SYSTEMS IMPLEMENTATION AND
CONVERSION
• Three types of documentation must be
prepared for new systems:
– Development documentation
• Describes the AIS and includes:
–
–
–
–
–
A system description.
Copies of output, input, file, and database layouts.
Program flowcharts.
Test results.
User acceptance forms.
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SYSTEMS IMPLEMENTATION AND
CONVERSION
• Three types of documentation must be
prepared for new systems:
– Development documentation
– Operations documentation
• Includes:
– Operating schedules.
– Files and databases accessed.
– Equipment, security, and file retention requirements
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SYSTEMS IMPLEMENTATION AND
CONVERSION
• Three types of documentation must be
prepared for new systems:
– Development documentation
– Operations documentation
– User documentation
• Teaches users how to operate the AIS.
• Includes a procedures manual and training materials.
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Systems
Analysis
Conceptual
Systems
Design
Physical
Systems
Design
Implementation
Planning
Prepare site;
Install and Test
Hardware
Complete
Documentation
Conversion
Select and Train
Personnel
Test
System
Operation
and
Maintenance
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SYSTEMS IMPLEMENTATION AND
CONVERSION
• Test the system
– Inadequate system testing has contributed to the
failure of systems.
– All of the following should be given a trial run in
realistic circumstances.
•
•
•
•
•
Documents and reports
User input
Operating and control procedures
Processing procedures
Computer programs
– Should also test:
• Capacity limits
• Backup and recovery procedures
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SYSTEMS IMPLEMENTATION AND
CONVERSION
• Three common forms of testing include:
– Walk-throughs
• Step-by-step reviews of procedures or program logic.
– Attended by the development team and users early in system
design.
– Focus is on organization:
• Input
• Files
• Outputs
• Data flows
– Subsequent walk-throughs are attended by programmers.
• Address logical and structural aspects of program code.
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SYSTEMS IMPLEMENTATION AND
CONVERSION
• Three common forms of testing include:
– Walk-throughs
– Processing test transactions
• Determines whether the program operates as
designed.
• Requires both valid and erroneous data.
• The correct response for each test should be
specified in advance.
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SYSTEMS IMPLEMENTATION AND
CONVERSION
• Three common forms of testing include:
– Walk-throughs
– Processing test transactions
– Acceptance tests
• Uses copies of real transactions and files
rather than hypothetical ones.
– Users develop acceptance criteria.
– Then make final decision whether to accept.
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SYSTEMS IMPLEMENTATION AND
CONVERSION
• Three common forms of testing include:
– Walk-throughs
– Processing test transactions
– Acceptance tests
• Even software purchased from an
outside vendor must be tested
thoroughly before installation.
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Systems
Analysis
Conceptual
Systems
Design
Physical
Systems
Design
Implementation
Planning
Prepare site;
Install and test
hardware
Complete
documentation
Conversion
Select and Train
Personnel
Test
system
Operation
and
Maintenance
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SYSTEMS IMPLEMENTATION AND
CONVERSION
• Systems conversion
– Conversion is the process of changing from the old
AIS to the new.
– Many elements must be converted, including:
•
•
•
•
Hardware
Software
Data files
Procedures
– The process is complete when the new AIS has
become a routine, ongoing part of the system.
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SYSTEMS IMPLEMENTATION AND
CONVERSION
• Conversion approaches
– Four conversion approaches are used to
change from an old to a new system:
•
•
•
•
Direct conversion
Parallel conversion
Phase-in conversion
Pilot conversion
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SYSTEMS IMPLEMENTATION AND
CONVERSION
• Conversion approaches
– Four conversion approaches are used to
change from an old to a new system:
•
•
•
•
Direct conversion
Parallel conversion
Phase-in conversion
Pilot conversion
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SYSTEMS IMPLEMENTATION AND
CONVERSION
• Direct conversion
– Immediately terminates the old AIS when the
new one is introduced.
– Appropriate when:
• The old AIS has no value; or
• The new AIS is so different that comparisons
between the two are meaningless.
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SYSTEMS IMPLEMENTATION AND
CONVERSION
• Main advantage to direct conversion:
– It’s inexpensive
• Main disadvantage:
– It provides no backup AIS.
• There is a high risk of failure unless the
new system has been very carefully
developed and tested.
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SYSTEMS IMPLEMENTATION AND
CONVERSION
• Conversion approaches
– Four conversion approaches are used to
change from an old to a new system:
•
•
•
•
Direct conversion
Parallel conversion
Phase-in conversion
Pilot conversion
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SYSTEMS IMPLEMENTATION AND
CONVERSION
• Parallel conversion
– Operates the old and new systems
simultaneously for a period of time.
– You can process transactions with both
systems, compare output, reconcile
differences, and make corrections to the new
AIS.
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SYSTEMS IMPLEMENTATION AND
CONVERSION
• Main advantage to parallel conversion:
– It protects the company from errors.
• Main disadvantage:
– It is costly and stressful for employees to process all
transactions twice.
• Because companies often experience problems
during conversion, parallel processing has
gained widespread popularity.
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SYSTEMS IMPLEMENTATION AND
CONVERSION
• Conversion approaches
– Four conversion approaches are used to
change from an old to a new system:
•
•
•
•
Direct conversion
Parallel conversion
Phase-in conversion
Pilot conversion
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SYSTEMS IMPLEMENTATION AND
CONVERSION
• Phase-in conversion
– Gradually replaces elements of the old AIS with the
new one.
– The new system is often phased in a module at a
time.
– Main Advantage:
• Data processing resources can be acquired over time.
– Disadvantages:
• Costs of creating temporary interfaces between old and new
AIS.
• Time required to make the complete conversion.
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SYSTEMS IMPLEMENTATION AND
CONVERSION
• Conversion approaches
– Four conversion approaches are used to
change from an old to a new system:
•
•
•
•
Direct conversion
Parallel conversion
Phase-in conversion
Pilot conversion
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SYSTEMS IMPLEMENTATION AND
CONVERSION
• Pilot conversion
– Implements a system in just one part of the
organization, e.g., a branch office or a single store.
– When problems with the system are resolved, the
new system could be implemented at the remaining
locations.
– Advantages:
• Localizes conversion problems and allows training in a live
environment.
– Disadvantages:
• Long conversion time.
• Need for interfaces between old and new systems.
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SYSTEMS IMPLEMENTATION AND
CONVERSION
• Data conversion
– Data conversion can be time-consuming,
tedious, and expense.
– The difficulty and magnitude is easy to
underestimate.
– Data files may need to be modified in three
ways:
• Files may be moved to a different storage medium
(e.g., tape to disk).
• Data content may be changed (e.g., fields added
or deleted).
• A file or database format may be changed.
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SYSTEMS IMPLEMENTATION AND
CONVERSION
• Steps in the data conversion process:
– Decide which data files need to be converted.
– Check files for completeness and data inaccuracies,
and remove any inconsistencies.
– Do the actual data conversion.
– Validate the new files to ensure data were not lost
during conversion.
– If the file conversion is lengthy, update the new files
with transactions that occurred during data
conversion.
– After conversion and testing, monitor the system to
make sure it runs smoothly and accurately.
– Document the conversion activities.
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Systems
Analysis
Conceptual
Systems
Design
Physical
Design
Implementation
and
Conversion
Operation
and
Maintenance
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OPERATIONS AND MAINTENANCE
• The last step in the SDLC is to operate
and maintain the new system.
• A post-implementation review should be
conducted to ensure the new AIS meets its
planned objectives.
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OPERATIONS AND MAINTENANCE
• Factors and questions include:
– Goals and objectives
• Does the system help the organization meet its goals,
objectives, and overall mission?
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OPERATIONS AND MAINTENANCE
• Factors and questions include:
– Goals and objectives
– Satisfaction
• Are users satisfied?
• Do they want changes or improvements?
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OPERATIONS AND MAINTENANCE
• Factors and questions include:
– Goals and objectives
– Satisfaction
– Benefits • Were the expected benefits achieved?
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OPERATIONS AND MAINTENANCE
• Factors and questions include:
– Goals and objectives
– Satisfaction
– Benefits
– Costs • Are actual costs in line with expected costs?
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OPERATIONS AND MAINTENANCE
• Factors and questions include:
– Goals and objectives
– Satisfaction
– Benefits
– Costs
– Reliability
• Has the system failed, and if so, why?
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OPERATIONS AND MAINTENANCE
• Factors and questions include:
– Goals and objectives
– Satisfaction
– Benefits
– Costs
– Reliability
– Accuracy
• Does the system produce accurate and complete
data?
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OPERATIONS AND MAINTENANCE
• Factors and questions include:
– Goals and objectives
– Satisfaction
– Benefits
– Costs
– Reliability
– Accuracy
• Does the system produce timely information?
– Timeliness
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OPERATIONS AND MAINTENANCE
• Factors and questions include:
– Compatibility
 Are hardware, software, data, and procedures
compatible with existing systems?
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OPERATIONS AND MAINTENANCE
• Factors and questions include:
– Compatibility
– Controls and security
 Are there safeguards against unintentional errors,
fraud, and intrusion?
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OPERATIONS AND MAINTENANCE
• Factors and questions include:
– Compatibility
– Controls and security
– Errors
 Are there adequate error-handling procedures?
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OPERATIONS AND MAINTENANCE
• Factors and questions include:
– Compatibility
– Controls and security
– Errors
– Training
• Are systems personnel and users adequately
trained?
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OPERATIONS AND MAINTENANCE
• Factors and questions include:
– Compatibility
– Controls and security
– Errors
– Training
– Communications
• Is the communications system adequate?
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OPERATIONS AND MAINTENANCE
• Factors and questions include:
– Compatibility
– Controls and security
– Errors
• Are structural changes that resulted from the system
– Training
beneficial or harmful?
• If harmful, how can they be resolved?
– Communications
– Organization changes
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OPERATIONS AND MAINTENANCE
• Factors and questions include:
– Compatibility
– Controls and security
– Errors
– Training
– Communications
• Is documentation
– Organization
changescomplete and accurate?
– Documentation
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OPERATIONS AND MAINTENANCE
• Any problems discovered during the
review should be brought to
management’s attention, and adjustments
should be made.
• When the review is complete, a postimplementation review report is
prepared.
• User acceptance of that report is the final
activity in systems development.
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OPERATIONS AND MAINTENANCE
• Control of the AIS is then passed to the
data processing department.
• But the work is not done.
– About 30% of the work takes place during
development.
– The remaining 70% is spent in maintaining
the system—particularly with respect to
software modifications and updates.
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SUMMARY AND CONCLUSIONS
• You’ve learned in more depth about the activities
that take place in the conceptual design phase of
the systems development life cycle (SDLC).
• You’ve also learned about activities that take
place in the physical systems design phase.
• You’ve explored what happens during the
systems implementation and conversion
process.
• Finally, you’ve learned about the activities in the
last phase of the systems development life
cycle—the systems operation and maintenance
process.
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