SYSTEMS DEVELOPMENT LIFE CYCLE (SDLC) SS2 2ND TERM

Introduction: 

Systems development is a planned undertaking with a fixed beginning and end that produces the desired result or product. It may be a large job that involves many people working

for a long period or it can also be a small assignment that one person can finish in a day. 

The SDLC provides an overall formalized method for managing the systems development processes and activities. It represents a detailed and specific set of procedures, steps, and documents that are required for the development of an information system. It describes the stages involved in an information system Development.

The SDLC believes that the development of information systems should follow a structured and methodical way, requiring each stage of the life cycle from inception of the idea to delivery of the final system, to be carried out in rigid and sequential order.

Note that: the Systems Development Life Cycle and Systems Development Cycle mean the same and can be used interchangeably.

DEFINITIONS OF SDLC:

1. The systems development life cycle is the process of understanding how an information system (IS) can support the business needs of an organization, designing the system, building it and delivering it to the users.

2. System development Life Cycle (SDLC) is a conceptual model in project management that describes the stages in an information system development project.

3. The system development life cycle can be defined as a project management technique that divides complex projects into smaller, more manageable segments or phases.

4. System development life cycle is an organisational process of developing and maintaining systems. It means a combination of various activities.

Objectives Of SDLC

A system development life cycle has three primary objectives: 

i. To ensure that high quality systems are delivered, 

ii. to provide strong management controls over the projects, and 

iii. to maximize the productivity of the systems staff.

SYSTEMS DEVELOPMENT CYCLE METHODOLOGIES

1. Waterfall model (original method)

2. Rapid Application Development (RAD)

3. Joint Application Development (JAD)

4. Fountain Model

5. Spiral Model.

Mostly, several models are combined into some set of hybrid methodology.

Requirements of System Development Life Cycle

 In order to make the above objectives work, system development life cycle has many specific requirements it must meet. These include:

i. ability to support projects and system of various scope

ii. it must be able to support all the technical activities like system definition, testing, installation, production and support, etc.

III. it must be highly stable 

iv. It must provide guidance on how to install it

STAGES IN SYSTEMS DEVELOPMENT CYCLE (SDC)

There are methods for developing information systems. The oldest and classical method of Systems Development Life Cycle (SDLC) is called the Waterfall Model. The Waterfall SDLC is a sequence of stages that must be followed one after the other. 

The following are stages of system development life cycle:

1. Preliminary study

2. Feasibility study 

3. Detailed or Investigative system study

4. System analysis 

5. System design

6. Implementation 

7. Maintenance 

8. Study review

 Description of each Stage

Preliminary study

This is the first stage of the system development life cycle. It is a brief investigation of the system under consideration and give a clear picture of what actually the physical system is. The initial system study involves the preparation of a system proposal which list the problem definition, objectives of the study, terms and reference of study, constraints, and the expected benefits of the new system, etc.

Feasibility study

In case the proposal is acceptable to the management, the next stage is to examine is the Feasibility study. Feasibility study is basically the test of the proposed system in the light of workability, meeting user’s requirements, effective use of resources and the cost effectiveness.

Detailed/Investigative study

This involves detailed study of various operations performed by a system and their relationships within and outside the system. During this process, data are collected on available files, decision points and transaction handled by the present system. Interviews, on-site interviews and questionnaires are the tools used for detailed system study.

System analysis

System analysis is a process of collecting factual data, understanding the process involved, identifying problems and recommending feasible suggestions for improving the functional system. The major objectives of system analysis are to find answers for each process. What is been done, how it is being done, who is doing it, when is he doing it, why is it being done, and how can it be improved.

System Design

Based on the user requirements and the detailed analysis of the existing system, the new system must be designed. This is the phase of system designing. It is the most crucial phase in the developments of a system. The tools and techniques used for describing the system designs are:

1. Flowchart

2. Data flow diagram

3. Data dictionary

4. Decision table 

5. Decision tree. 

The system design involves:

Defining the required system output 

Determine the data required for producing the output 

Devising processing methods and use of software to produce the output

Determine the methods of data capture and data input 

Designing input forms designing codification schemes

Documenting the design

Testing: this is an important phase of the successful system. After codifying the whole program of the system, a test plan should be developed and run on a given set of test data. The output of the test run should match the expected results. 

Sometimes the system testing is considered a part of implementation process. There are two categories of test:

1. Program test

2. System test

Implementation

After having the user acceptance of the new system developed, the implementation phase begins. Implementation is the stage of a project during which theory is turned into practice. The major steps involved in this phase are:

Acquisition and Installation of Hardware and Software

Conversion

User Training

Documentation

After the users have been trained by the new system, working has to shift from manual to computerized system. This process is called Change Over.

The following strategies are followed for the changeover of system:

1. Direct Changeover

This is the complete replacement of the old system by the new system. Basically, as soon as the new system is powered up, the old system is shut down. This type of changeover carries the most risk because, if something goes wrong, reverting back to the old system usually is impossible.

2. Parallel run

In parallel run the system, that is, computerized and manual are executed simultaneously for certain definite period. Of all the techniques, this tends to be the most popular, mainly because it carries the lowest risk. If something goes wrong at any point, the entire system can be reverted back to its original state.

3. Pilot Run

With a pilot changeover, the new system is tried out at a test site before launching it company-wide. For example, a bank may first test the system at one of its branches. This branch is referred to as the pilot. Since parallel changeovers tend to be expensive, using the pilot changeover technique allows companies to run the new system next to their old but on a much smaller scale.

Maintenance

Maintenance is necessary to eliminate errors in the system during its working life and to tune the system to any variation in its working environments. It also means the review of the system from time to time.

System /Study Review

Review activities occur several times throughout this phase. Each time the system is reviewed, one of three of the following decision will be made:

The system is operating as intended and meeting performance expectations

The system is not operating as intended and needs corrections and modifications

Users are/are not satisfied with the operation and performance of the system.

In this process review is performed to evaluate the system performance, user's satisfaction with the system, adaptability to changing business needs, and new technologies that might improve the system. 

If a major change to a system is needed, a new project may have to be set up to carry out the change. The new project will then proceed through all the above life cycle phases.

Diagram of System Development Life Cycle

The diagram below shows the development life cycle.

System Proposal:

This is prepared by the System Analyst who studies the system and places it before the user and the management for consideration.

ADVANTAGES OF SDLC

The advantages of SDLC are:

1. Simple and easy to use

2. Easy to manage due to the rigidity of the model. 

3. Phases are processed and completed one at a time. It works well for developing small information systems where requirements are very well understood. 

4. It provides guidelines for systems development as all the stages and activities are clearly Outlined.

5. Promotes consistency among system development projects.

6. Reduces cost of managing different systems at different stages.

7. Helps in efficient allocation of resources to systems development projects.

DISADVANTAGES OF SDLC

The disadvantages of SDLC are:

1. Adjusting scope during the life cycle can kill a project 

2. No working software is produced until late during the life cycle

3. High amounts of risk and uncertainty 

4. Poor model for complex and object–oriented projects 

5. Poor model for long and ongoing projects 

6. Poor model where requirements are at a moderate to high risk of changing 

7. It takes time to go through the whole long development cycle.