Data management a brief history

What is data, database system DBS and DBMS?

Data  is collection of raw facts and figures. It may exist in any form i.e text, image, sound, and video. It is usually meaningless unless it is processed. After processing data becomes information which is more meaningful than data.

Since information is generated from data, therefore data is big asset of any organization. In the early days of computer, file processing system had been used for data management. For many years, it remained as the only choice for data management but with the passage of time it lost its popularity. The reason was its failure to resolve novel issues like transparency, concurrency, redundancy and data protection. That is why it was replaced by database systems.

What is a database?

Database can be defined as “an organized collection of interrelated data”.
In file processing system, data was application (or program) dependent. Each file needed a specific program to open it. For example, an excel file could only be opened by MS Excel. But, in a database system, data is no more bound to a specific application i.e data may be read by any application.
 DBMS (database management system) is the software that is used to design and maintain a database. It provides an interface between user and database.

File Processing System Vs DBMS

File processing system does not know the structure of data while DBMS knows that.
File processing system provides simple access to data while DBMS provides a programmatic way like queries to access data.
A file system controls only physical access to data while a database management system controls both the physical and the logical access to the data.
A file processing system provides predetermined (fixed) access to data while a database management system allows flexible access to data (i.e. queries)
A file processing system allows concurrent access to data on a limited scale. For example, a file can be accessed by more than one programs, only if they have read-only access, while a database management system can allow several users to access even a piece of data at the same time.
File processing system can’t restrict unauthorized access to data while DBMS has full protection mechanisms to permit or restrict users.
File processing can’t stop redundancy; for example multiple copies of same data may be created without any objection from file processing system side, while DBMS has full redundancy control mechanism.
File processing system has no way to recover lost data while DBMS provide backup and recovery techniques to save data losses.
In file processing system, data is dependent on program; for example excel file can only be opened by Excel program, but a DBMS provides program data independence. DBMS eliminates data dependence over specific programs.

Database models

A conceptual framework of database is called database model. There are basically two database models
Relational model
Object oriented model
Object-Relational (relational + object oriented)
Relational data model
Relational model is a primary model for data storage and processing. It was proposed by E. F. Codd in 1969. He suggested using relations for data storage and a query language SQL for its processing.
Relations are just like a table (2-dimensional data structure).
Each row of a relation is called tuple
Each column of a relation is called field
Intersection of column and row is cell
A cell may contain only atomic value.
Two relations are associated by primary key/foreign key relationship
Primary key can’t contain null value
Foreign key must match corresponding primary key value.
SQL is a standard query language for data processing
 Conceptual Schema of relation: It refers to the structure of a relation like filed names and their types. e.g. STUDENT(id as int, sname as varchar(20), fname as varchar(20), ………………..)

RDBMS

RDBMS is database management system DBMS that is based on relational model invented by E.F. Codd in 1969. It is a popular DBMS all over the world. It is a common choice for all kinds of applications:
Small or large scale applications
Personal or business application
Some important RDBMS are like Access, Oracle, MySQL, SQL Server, PostgreSQL,DB2

RDBS

A database system using RDBMS as database model is called relational database system.
Database System:  DBS=Database + DBMS
Types of Database Systems
On the basis of physical distribution of data, there are two types of database systems
Centralized database systems: CDBS
Distributed database systems: DDBS
Centralized database system
A single database maintained on one location.
Managed by a database administrator. (usually )
Access via a communications network
LAN
WAN
Terminals may provide distributed access
Examples
Banks
Airline reservation systems need to be centralized to avoid double bookings.
Police and ambulance calls centers.
Advantages
Increased reliability and availability
Modular (incremental) growth
Lower communication costs
Faster Response
Disadvantages
Software cost and complexity
Processing overheads
Data integrity