A Database is an organized collection of logically related data. The purpose of database is to store information about certain types of objects termed entities or objects.
A database is a shared collection of logically related data designed to meet the information needs of an organization.
Components of Database Systems
- Database
- Hardware
- Software – DBMS
- Procedures
- Users
- Database
The data in the database will be expected to be both integrated and shared particularly on multi-user systems
Integration – The database may be thought of as a unification of several otherwise distinct files, with any redundancy among these files eliminated
Shared – individual pieces of data in the database may be shared among several different users
- Data: Refers to stored representations of meaningful objects and events. Includes Structured: numbers, text, dates
- Unstructured (multimedia): images, video, documents
- Information: Refers to data processed to increase knowledge of the person who uses the data place data in a context
- Involves summarizing, processing and presentation of data
- Metadata-Is data that describes the properties or characteristics of user data.It is the primary mechanism for providing context for data.Data without metadata can be confusing, misinterpreted, or erroneous
2.Hardware
These are secondary storage on which the database physically resides, together with the associated I/O devices, device controllers etc.
3.Procedures
These are instructions and rules that govern design and use of databases e.g. starting and stopping database, making backups, handling failures.
4. Users and their Roles
- Database Designers – designs conceptual and logical database
- Application Developers – writes application programs that use the database
- Data and Database Administrator
- End – user – interacts with the system from an on-line terminal by using Query Languages etc.
- Data Administrator – Is a business manager responsible for controlling the overall corporate data resources
- Database Administrator (DBA) – Is a technical person responsible for development of the total system
- Program-data independence: the separation of data description from the application program; metadata is stored in central repository
- Planned data redundancy: Control of data redundancy
- Improved data consistency
- Improved data sharing and productivity
- User view: a logical description of some portion of the database that is required by a user to perform some task
- Increased application development productivity
- Enforcement of standards
- Naming conventions, data quality standards and uniform procedures for accessing, updating and protecting data
- Improved data quality
- Integrity constraints
- Improved data accessibility and responsiveness
- SQL (structured query language) can be used to extract meaning from data.
- Reduced program maintenance
- Improved decision support
- Multipurpose use of data
- Balance conflicting user requirement
- Improved data accessibility and responsiveness
- Improved maintenance through data independence
- Increased concurrency
- Improved backup and recovery services.
- Complexity
- Size
- Cost of DBMS : Installation and management cost and complexity
- Additional hardware costs
- New, specialized personnel
- Conversion costs
- Need for explicit backup and recovery
- Organizational conflict.