Ø DBMS
- A database management system
(DBMS) is system software for creating and managing databases. The DBMS provides
users and programmers with a systematic way to create, retrieve, update and
manage data.
OR
Ø
A Database is
a collection of related data organised in a way that data can be easily
accessed, managed and updated. Database can be software based or hardware
based, with one sole purpose, storing data.
Here are some examples
of popular DBMS used these days:
- MySql
- Oracle
- SQL Server
- IBM DB2
- PostgreSQL
- Amazon SimpleDB (cloud based) etc.
Ø Characteristic of DBMS – A modern DBMS has the following characteristics –
1.
Real-world entity
2.
Relation-based tables
3.
Isolation of data and
application
4.
Less redundancy
5.
Consistency
6.
Query Language
7.
ACID Properties
8.
Multiuser and
Concurrent Access
9.
Multiple views
10. Security
1) Real-world entity –
·
A DBMS is more realistic and uses real-world
entities to design its architecture.
·
It uses the behaviour
and attributes too.
·
For example, a school database may use
students as an entity and their age as an attribute.
2) Relation-based tables –
·
DBMS allows entities
and relations among them to form tables.
·
A user can understand
the architecture of a database just by looking at the table names.
3) Isolation of data and application –
·
A database is an
active entity, whereas data is said to be passive, on which the database works
and organizes.
·
DBMS also stores metadata, which is data about
data, to ease its own process.
4) Less redundancy − DBMS follows
the rules of normalization, which splits a relation when any of its attributes
is having redundancy .
5) Consistency –
·
Consistency is a
state where every relation in a database remains consistent.
·
There exist methods
and techniques, which can detect attempt of leaving database in inconsistent
state.
·
A DBMS can provide greater consistency as
compared to earlier forms of data storing applications like file-processing
systems.
6) Query Language –
·
DBMS is a query
language, which makes it more efficient to retrieve and manipulate data.
·
Traditionally it was
not possible where file-processing system was used.
7) ACID Properties –
·
DBMS follows the
concepts of Atomicity, Consistency, Isolation,
and Durability (normally shortened as ACID).
·
These concepts are
applied on transactions, which manipulate data in a database.
·
ACID properties help the database stay healthy
in multi-transactional environments and in case of failure.
8) Multiuser and Concurrent Access –
·
DBMS supports
multi-user environment and allows them to access and manipulate data in
parallel.
·
Though there are
restrictions on transactions when users attempt to handle the same data item,
but users are always unaware of them.
9) Multiple views − DBMS offers
multiple views for different users.
10)Security − DBMS offers
many different levels of security features, which enables multiple users to
have different views with different features.