- Database Management System
Database Management System
A database management system is a collection of interrelated data and a set of programs to access those data. It manages new large amount of data and supports efficient access to new large amounts of data.
Data
Known facts that can be stored or recorded is called data.
It can be of two types
Persistent Data It continues to exist even. when the system is not active.
Transient Data It created while an application is running and not needed, the application has terminated. It must be stored in secondary memory.
Database
Database is a collection of related data with
- A logically coherent structure (can be characterised as a whole).
- Some inherent meaning (represents some partial view of a portion of the real
- Some specific purpose and for an intended group of users and
- A largely varying size (from a personal phone book directory to the phone book directory of a city or state).
- A Scope Or content of varying breadth (from a personal list of addresses to a multimedia encyclopedia).
- A physical organization of varying complexity (from a manual personal list, managed with simple files, to huge multiuser databases with geographically distributed data and access).
Formal Definition of Data
Logically coordinated obiectives, data is defined once for a community of
User and accessed by various applications with specific needs.
The information contained in a database is represented on two levels –
- Data (which is large and is being frequently modified)
- (ii) Structure of data (which is small and stable in time)
Basic Concept of DBMS
It is a collection of general purpose, application independent programs
providing services to
- Define the structure of a database, i.e., data types and constraints that thE data will have to satisfy.
- Manage the storage of data, safely for long periods of time, on some
storage medium controlled by the DBMS.
changes in the world, generate reports from the data.
- Manipulate a database with efficient user interfaces to query the database to retrieve specific data, update the database to reflect change in the world, generate reports from the data.
- Manage database usage for users with their access rights, performance optimization, sharing of data among several form accidents or unauthorised use .
- monitor and analyse database usage,
Database Management System (DBMS) provides efficient, reliable, convenient and safe multiuser storage of and access to massive amounts of persistent data.
Key People Involved in a DBMS
The followings are the key people involved in a DBMS as
DBMS Implementer Person who builds system.
Database Designer
Person responsible for preparing external schemas for applications, identifying and integrating user needs into a conceptual (or community or
enterprise) schema.
Database Application Developer
Person responsible for implementing database application programs that facilitate data access for end users.
Database Administrator
Person responsible for define the internal schema, sub-schemas (with database designers) and specifying mappings between schemas, monitoring database usage and supervising DBMS functionality (e.g., access control, performance optimisation, backup and recovery policies, conflict management).
End Users
There are two categories of end users
- Casual users Occasional unanticipated access to database. e.g., tourists, managers.