Unit 9


Unit 9: System Development Life Cycle - Investigat

The System Development Life Cycle is used in the development of new systems or when modifying already existing ones. 

1. Investigation
Involves the analysis of the existing system (if one) producing feasibility report. Includes:

  • Existing hardware and software - does the hardware and software need upgrading
  • Current problems - what should the new system solve
  • User requirements - agreement between developer and end users about what the system needs to be able to do.
  • Costs and benefits of new system - hardware, software, training costs. Benefits may include; accuracy of information, time saving and more detailed analysis of data.
  • Major data processing functions and processes - showing data flows between system and other organisations' systems. (Shown using a flow diagram)
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Unit 9: System Development Life Cycle - Analysis

2. Analysis

In order to understand and analyse the current system the following tools and techniques are used: 

  • Interviews - speaking to managers about how company works and the user requirements
  • Observation - shadowing employeesto find out what their jobs involve. It can be time consuming to observe every part of the system.
  • Inspection of Records - current paper informaion produced such as organisational charts.
  • Questionnaires -quick and easy to distribute but employees may not filll them in giving an incomplete picture.

Using the information gathered using the tools and techniques a solution is set out.

Producing a specification to be used in the development of the system.

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Unit 9: System Development Life Cycle - Design

3. Design

  • Design of hardware - choosing computer equipment which is powerful enough for the tasks to be undertaken.
  • Design of software -ensuring that all software is compatible with the hardware and operating system that is chosen.
  • Design of data and file structures -think about the design of the fields and table structure for a relational database in order to allow a useable system to be built.
  • Design of Information Systems - users need to be able to obtain information from the system that is useful in order to allow them to make appropriate decisions.
  • Design of network and data transmission - appropriate network topology must be chosen & many factors must be considered including choice of network cable & protocols 
  • Design of Personnel - needs to be provision for staff training that is matched to the skill level of the user. Some departments need reorganising. 
  • Design of security processes - issues such as registration with Data Protection Act Information Commisioner: setting up access levels, managing data storage and creatng backup policies. 
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Unit 9: System Development Life Cycle - Implementa

4. Implementation

This is where the design of the system is put into practice, including:

  • Aquisition of hardware and software - purchasing the computer equipment and software that was listed in the design specification. 
  • Installation of hardware and software - installing the hardware and software, at off-peak periods to minimise the disruption caused.
  • Retraining - staff will now be shown how to use the new computer and software.

The new system is introduced via changeover strategy. two types; parallel running/ direct.

Parallel - old system stays running alongside new one until working. Both systems can be compared to ensure working. However, some work is duplicated as two systems are working.

Direct -old system is turned off and new system is turned on next day. This is good as saves time and money running 2 systems. However, risky with new hardware, if doesnt work business can be lost.

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Unit 9: System Development Life Cycle - Maintenanc

5. Maintenance

Once the system has been introuduced it needs to be maintained to prevent problems occuring. Some common maintenance issues include:

  • Identification errors - could contain 'bugs' or mistake in the coding if its not tested well.
  • Security issues - any weak points in the system could be targeted by viruses or hackers.
  • Changes in the business environment - downsizing or expanding will mean a change in the roll of the company and system changes will need to reflect this.
  • Dissatisfaction with hardware and software - software may not carry out the tasks that it is required to and system hardware may process data to slowly.
  • Updating the system - if new hardware or software is made available by technological developments, then all the system needs to be updated.

Two documents are created in order to help employees change over smoothly to the new system: User documentation and technical documentation.

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Unit 9: System Development Life Cycle - Evaluation

6. Evaluation

Review how sucessful/ unsucessful the implementation has been. Evaluation criteria includes:

  • Satisfaction of end users - happy with what the system allows them to do.
  • Original user requirements - are problems with the old system addressed in new one.
  • Reliability - is the system working most of the time or does it constantly crash.
  • Security - has the new system experienced any breaches of security - e.g. hackers.

An evaluation report will be produced on how effective the implentation of the new system has been. Several tools are used for gathering information for the report:

  • Quantative testing -quality of system numerically - user scores the system on a scale or statistical tools like averages can then be applied to responses.
  • Error logging Interviews - calls to the ICT helpdesk are logged to keep track of how many crashes occur and the usability of the system.
  • Questionnaires - satisfaction with the system.
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Unit 9: SDLC - Costs Occured

When implementing the new system, a number of post implementation costs occur. There are however methods of preventing these costs such as;

Training costs - initial training should be detailed to avoid having to pay for more training later.

Support costs - detailed training of staff and fully tested hardware/software will reduce the amount of support needed.

Maintenance costs - the high cost of corrective maintenance can be avoided if a thorough test plan is carried out.

Hardware costs - the hardware purhcased needs to allow for further expansion. This will avoid having to purchase additional storage if the initial storage becomes full.

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