What is DBMS?

• A DBMS is a system software package that helps the use of integrated collection of data records and files known as databases. It allows different user application programs to easily access the same database.

• Data base management system is the system in which related data is stored in an "efficient" and "compact" manner. Efficient means that the data which is stored in the DBMS is accessed in very quick time and compact means that the data which is stored in DBMS covers very less space in computer's memory. In above definition the phrase "related data" is used which means that the data which is stored in DBMS is about some particular topic.

Components of DBMS

Transaction Management

• A transaction is a sequence of database operations that represents a logical unit of work and that accesses a database and transforms it from one state to another.

• A transition can update a record, delete (or) modify a set of records etc.

Concurrency control

Concurrency control is the database management activity of co-ordinating the actions of database manipulating process that separate concurrently that access shared data and can potentially interfere with one another.

Recovery Management

The recovery management system in a database ensures that the aborted or failed transactions create non adverse effect on the database or the other transitions.

Security Management

Security refers to the protection of data against unauthorized access. Security mechanism of a DBMS make sure that only authorized users are given access to the data in the database

Language Interface

The DBMS provides support languages used for the definition and manipulation of data in the database. The data structures are created using the data definition language commands. The data manipulation is done using the data manipulation commands.

Storage Management

The DBMS provides a mechanism for management of permanent storage of the data. The internal schema defines how the data should be stored by the storage management mechanism and this storage manager interface with the operating system to access the physical storage.

Data Catalog Management

Data catalog or Data Dictionary is a system database that contains descriptions of the data in the database (metadata). If contains information about data, relationships, constraints and the entire schema that organize these features in to a unified database.

Need For DBMS

• Data independence and efficient access.

• Reduced application development time.

• Data integrity and security.

• Uniform data administration.

• Concurrent access, recovery from crashes.