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The Information System Lifecycle
In a large organization, the database system is typically part of the Information system, which includes all resources that are involved in the collection, management, use and dissemination of the information resources of the organization. In a computerized environment these resources include the data itself, the database management system software, the computer systems hardware and storage media, the personnel who use and manage the data, the application software that accesses and updates the data and the application programmers who develop theses applications. Thus the database system is part of a much larger organizational information system.
Examining the typical lifecycle of an information system, it is often called the macro lifecycle, whereas the database system lifecycle is referred to as the micro lifecycle. The distinction between these two is becoming fuzzy for information systems whereas databases are a major integral component. The macro lifecycle typically includes the following phases:
- Feasibility Analysis
This phase is concerned with analyzing potential application areas, identifying the economics of gathering information and dissemination, performing preliminary cost-benefit studies, determining the complexity of data and processes, and setting up priorities among applications.
- Requirements collection and analysis
Detailed requirements are collected by interacting with potential users and user groups to identify their dependencies, communication, and reporting procedures are identified.
- Design
This phase has two aspects: the design of the database system, and the design of the application systems (programs) that uses and process the database.
- Implementation
The information system is implemented, the database is loaded, and the database transactions are implemented and tested.
- Validation and acceptance testing
The accessibility of the system in meeting user’ requirements and performance criteria is validated. The system is tested against performance criteria and behavior specifications.
- Deployment, operation and maintenance
This may be preceded by conversion of users from an older system as well as by user training. The operational phase starts when all system functions are operational and have been validated. As new requirements or applications crop up, they pass through all the previous phases until they are validated and incorporated into the system. Monitoring of system performance and system maintenance are important activities during the operational phase.
The Database application system lifecycle
Activities related to database application system (micro) lifecycle includes the following:
- System Definition
The database system’s scope , its users and its application are defined. The interfaces for various categories of users, the response time constraints, and storage and processing needs are identified.
- Database Design
At the end of this phase, a complete logical and physical design of the database system on the chosen database management system is ready.
- Database implementation
This consists of creation of empty database files along with few database definitions
- Loading or data conversion
Population of the database by direct data loading or file conversion of existing files into database system.
- Application conversion
Any software applications from a previous system are converted to the new system.
- Testing and Validation
The new system is tested and validated.
- Operation
Operation of the database system and applications is done here. Usually, the old and the new system are operated in parallel for some time.
- Monitoring and Maintenance
The system is constantly monitored and maintained during the operational phases. Growth and expansion occurs in both data contents and software applications. Major modifications and reorganization may be needed from time to time.
Activities like Database Design, Database implementation and Loading or data conversion together are part of the design and implementation phase of the larger information system life cycle. Most databases in organizations undergo all of the preceding life-cycle activities. The conversion activities are not applicable when both the database and the applications are new. When an organization moves from an established system to a new one activities like Loading or data conversion and Application conversion tend to be the most time-consuming and the effort to accomplish them is often underestimated.
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