Transcript SDLC: Development Phase

SDLC: Development Phase
Software Development
Unit 2 2010
Software Development consists of:
• Acquiring the Hardware
• Acquiring the Software
• Testing the System
SDLC: Implementation Phase
Implementation Phase
• Implementation consists of converting the old
system to the new system, which involves
converting hardware, software and any/all
associated files.
• Hardware conversion could involve replacing
or upgrading a computer or a number of
computers, replacing wiring/cabling, updating
security measures in buildings, etc.
• Software conversion – making sure that the
application (spreadsheet, database, etc.) that
worked on the old system, still works on the
new system.
• File conversion – (data conversion) –
converting the old files to the new ones
without loss. This includes the conversion of
paper-based files to electronic files.
There are 4 main conversion
methods:
Direct Approach(also known as Cut Over)
Users change directly and immediately from
the old system to the new
Advantages
• There is a fast and efficient change over
• Relatively cheap method
Disadvantages
• Staff can be alienated with the new system
• Can lead to loss of profits and productivity
if managed badly
Parallel Conversion (also known as
Parallel Systems)
All tasks are performed by both systems until the
new system is perfected
Advantages
• no loss of productivity of data
• staff become confident with the system because
there is time to be trained properly
• problems with new system are identified and
fixed before the old system is decommissioned
Disadvantages
• expensive to run two systems
• also time consuming to run two systems
• using two systems and be confusing
Phased In Conversion
Parts of the new system are introduced gradually
Advantages
• Problems with the new system can be fixed
before being fully implemented
• Staff that are part of the phased conversion can
be used to train other staff
• No loss of data
Disadvantages
• Can be a slow process to implement the
whole new system
• Mainly used in large organisations
• At times two systems (old and new) are
operated at the same time
Pilot Conversion
The entire system is tried out, but only by some users.
Once the reliability of the new system has been
proved, the system is implemented with the rest of
the intended users.
Advantages
• Reliability is established before full implementation
• Users who participate in the pilot can be used to
train the other staff
Disadvantages
• All users of a particular group are taken off
the old system to participate in the pilot
Other requirements to be considered
when implementing a new or modified
information system:
• Physical environment may need to be modified to
accommodate the new system.
• Support services will be required for the new system
eg. telephone help desk
• Consumables such as stationary, printer ink
cartridges, disks and disk storage facilities will need
to be purchased.
• Ergonomic requirements such as glare filters for
computer screens and tilt screens, higher desks, etc
will need to be attended to
Effects on Staff
• The implementation of a whole new system will
affect the staff who use the system.
• It may mean a change in their job roles and job
specifications, which in turn may lead to the
hiring of new staff with appropriate skills and
retraining current staff.
• The affect on staff needs to be carefully
managed as part of the implementation of the
new system.
Changes to Procedures
• When implementing a new system
some procedures that were used in the
old system might need to be changed in
the new system. Staff need to be made
familiar with these new procedures.
Error Procedure
• To identify the action to be taken the program
or hardware malfunctions
• To be a step-by-step guide to correct the
error
• To give advice on completing tasks manually
until the error is completed
Virus Detection Procedure
• To ensure against loss of data or functions
Startup Procedure
• To specify steps to be taken to start up
the system at the beginning of the day
or after a breakdown
Backup Procedure
• To ensure against physical damage or
accidental loss of data
The next part of implementation is to train
the users in how to use the new system.
Training is done using a variety of
tools/methods:
FORMAL TRAINING
• External: College and TAFE institutions
offer introductory short courses for
package software with an emphasis on
business applications.
• In-house: This is undertaken within the
organisation and uses its system. This
training is conducted by someone within the
organisation or by an outside expert. An
advantage of this type of training is that users
become familiar with the equipment and
procedures of the new system.
INFORMAL TRAINING
• Written materials: these come in the
form of manuals or tutorials that
accompany the software and hardware
components
• Computer-based training: most major
software packages provide a computerbased tutorial which leads the user
step-by-step through the major features
of the package
• General training: some large organisations
run seminars and conferences to promote
new or upcoming products. Designed mainly
for computing professionals.
• User groups: many groups have been
established to share and exchange
knowledge
• On-line services: These allow access to
user-pays information service from a
computer terminal through a modem
The methods of training listed above
normally cover the following areas
• Knowledge of the basic operations of the system
• Use of the procedures needed to operate the
system such as start up, shut down and backup
• Use of appropriate security techniques
• Knowledge of health and safety legislation for all
users
• Use of manuals for the software and hardware
• Evaluation of courses to determine future needs.
SDLC: Evaluation and
Maintenance Phase
Evaluation
The final phase of the system design life cycle is used
to evaluate the new or modified information system.
This phase involves monitoring, evaluating and
maintaining the system.
The system is evaluated to determine how effectively it
meets the objectives outlined in the preliminary
investigation.
• The objectives are assessed in three aspects;
performance; reliability and management of change:
Performance Evaluation
• The system manager/analyst is concerned with
evaluating the efficiency and productivity of the
technology. These characteristics can be measured
and compared to the estimates indicated in the
analysis and design phases.
• Efficiency is measured in terms of the time, cost and
effort to complete a set task eg. measure how long it
takes to print 18 pages of text.
• Productivity is concerned with the efficiency of the
overall process
Efficiency and productivity could be
evaluated in the following ways:
• Observing the system’s capacity to handle peak
periods of demand
• Surveying staff to determine tasks completed during
a set period, such as one day or one hour
• Timing the completion of a task
• Calculating the total cost of one working day
including wages, electricity and materials and then
comparing the same calculations with the old system
Reliability
• Many problems with a system only appear after a
system has been implemented. These can include faulty
equipment, inadequate training any incorrect
procedures. Procedures such as security, backup and
validation can be assessed in the following ways:
– Random shutdown of the system to determine if
processes can be carried out manually
– Removal of selected files to determine if backup
procedures are reliable
– Using computer professionals to test security
measures
Management of Change
• An essential part of evaluating a system is by
assessing the effects on job specifications, work
environment, etc. These changes can be monitored
in the following ways:
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Surveying staff reactions to the new system
Testing staff knowledge of the procedures
Monitoring frequency and cause of sick days
Assessing adequacy of training
Maintenance
• System maintenance adjusts and improves the
system by having system audits, user feedback and
periodic evaluations and by making changes based
on new conditions
• Maintenance includes not only keeping the
machinery running, but also updating and upgrading
the system to keep pace with new products, services,
customers, government regulations and other
requirements.
Costs and Benefits of Information
System
• A function in the evaluation phase is to
evaluate the overall costs and benefits of
the new system
Economic Costs
• Cost of new equipment
• Cost of employment of design team and computer
professionals
• Possible loss of production during the implementation
of the new system
• Disruption to staff and possible redundancy pay outs
• Cost of training
Economic Benefits
• Increased efficiency and productivity
• Improved quality control
• Improved customer service
Social Costs
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Repetitive strain injury
De-skilling of staff
Loss of employment
Stress due to change
Stress due to new technology
Social Benefits
• Increase in skill and job satisfaction
• Health and safety reforms
• Higher level of flexibility eg. flexible working hours