Definition:-
A Database Management Systems (DBMS) is a computer program designed to manage a database, a large set of structured data, and run operations on the data requested by numerous users.
Typical examples of DBMS are -: Accounting, human resources and customer support systems.
What is Database?
Database is a organized collection of data, Which can be easily accessed, managed and updated.
Example:- Dictionary, telephone directory
Types of Database:-
1. Distributed Database
2. Centralized Database
Distributed Database:-
A distributed database is a database in which portions of the database are stored in multiple physical locations and processing is distributed among multiple database nodes.
Centralized Database:-
A centralized distributed database management system (DBMS) integrates the data logically so it can be managed as if it were all stored in the same location. The DBMS synchronizes all the data periodically and ensures that updates and deletes performed on the data at one location will be automatically reflected in the data stored elsewhere.
Three layer Architecture of DBMS:-
From the above figure we classify that level of Data Abstraction in DBMS-
Data Store:-
Also known as physical storage and here we can store data.
Three Layers of Architecture are:-
1. Physical Level
2. Conceptual level
3. External level
Physical Level:-
It is the lowest layer of abstraction. It describes how data is stored in detail.
Conceptual Level:-
It is the level of abstraction and describes what data is stored and what relationship among data is. At the conceptual level, each such record is described by a type of definition and the interrelationship among those record types. Database administrators work at this level of abstraction.
External level:
It is the highest level of data abstraction and is defines by user. It describes part of entire database and hides the details of external level.
1). (a) Which Database is more secured?
Distributed Database
2). (b) Why?
Because distributed is at multiple locations where as centralized is at one location.
3). In which layer data structure is defined?
Physical level
4). Physical layer is also known as
Internal view
5). Which layer represents entire database?
Conceptual level
6). Which is closest to physical storage:
Internal view or physical level
7). ATM user and End user are examples of
External view or view level
8). Conceptual Level is also known as
Middle layer view (or) global view
9). Group of data is said to be:
Information
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