DBMS DBMS

By Narinder SinghBy Narinder Singh

Computer Sc. DepttComputer Sc. Deptt

Topics Topics

What is DBMSWhat is DBMS File System Approach: its limitationsFile System Approach: its limitations Why we need DBMS?Why we need DBMS? Difference between DBMS and Difference between DBMS and

Programming LanguagesProgramming Languages Difference between DBMS and Difference between DBMS and

RDBMSRDBMS Data Independence Data Independence

DBMSDBMS Database is collection of related Files.Database is collection of related Files. Database is organizing data into tabular form i.e. in the form Database is organizing data into tabular form i.e. in the form

of rows and columns.of rows and columns. A A Database Management SystemDatabase Management System ( (DBMSDBMS) is a set of ) is a set of

computer programs that controls the creation, maintenance, computer programs that controls the creation, maintenance, and the use of a database. and the use of a database.

It allows organizations to place control of database It allows organizations to place control of database development by database administrators (DBAs) and other development by database administrators (DBAs) and other specialists. specialists.

A DBMS is a system software package that helps the use of A DBMS is a system software package that helps the use of integrated collection of data records and files.integrated collection of data records and files.

It allows different user application programs to easily access It allows different user application programs to easily access the same database. the same database.

File System ApproachFile System Approach

Storing the data into a single file that is not Storing the data into a single file that is not linking with other file is the traditional file linking with other file is the traditional file system approach.system approach.

All the records resides in a single file leads to All the records resides in a single file leads to the problems such as data redundancy, the problems such as data redundancy, inconsistency etc. inconsistency etc.

Limitations of File System Limitations of File System ApproachApproach Separation and isolation of dataSeparation and isolation of data

-Difficult to access data that is available (eg. from two files – Student that achieved -Difficult to access data that is available (eg. from two files – Student that achieved good academic result and active in extra curriculum activities)good academic result and active in extra curriculum activities)

Duplication of dataDuplication of data-Cost time and money to enter data more than once-Cost time and money to enter data more than once-Additional storage space is needed - cost-Additional storage space is needed - cost-Inconsistencies of data-Inconsistencies of data

Data dependenceData dependence-File structure is defined in the program code.-File structure is defined in the program code.-Changes to an existing structure are difficult to make-Changes to an existing structure are difficult to make

Incompatible file formatsIncompatible file formats-Programs are written in different languages, and so cannot easily access each -Programs are written in different languages, and so cannot easily access each other’s files.other’s files.

Fixed Queries/Proliferation of application programsFixed Queries/Proliferation of application programs-Programs are written to satisfy particular functions.-Programs are written to satisfy particular functions.-Any new requirement needs a new program. -Any new requirement needs a new program.

Advantages of DBMSAdvantages of DBMS

Controlling redundancy Controlling redundancy Providing storage structure for efficient query Providing storage structure for efficient query

processing. processing. Restricting unauthorized users.Restricting unauthorized users. Providing concurrency. Providing concurrency. Providing backup and recovery. Providing backup and recovery. Enforcing integrity constraints. Enforcing integrity constraints. Improved data sharing.Improved data sharing.

Disadvantages of RBMSDisadvantages of RBMS Centralization: That is use of the same Centralization: That is use of the same

program at a time by many user sometimes program at a time by many user sometimes lead to loss of some data. lead to loss of some data.

High cost of software. High cost of software. Technical expertise are required.Technical expertise are required.

DBADBA

Database Administrator (DBA) is the Database Administrator (DBA) is the person(s) , who manages the database. person(s) , who manages the database.

Functions of DBA includesFunctions of DBA includes

1.1. Creation of database.Creation of database.

2.2. Decide Storage for the database.Decide Storage for the database.

3.3. Responsible for backup and recovery.Responsible for backup and recovery.

4.4. Create new users and assign privileges to Create new users and assign privileges to them.them.

DBMS vs RDBMSDBMS vs RDBMS DBMS has to be persistent, DBMS has to be persistent,

that is it should be that is it should be accessible when the accessible when the program created the data. A program created the data. A DBMS also has to provide DBMS also has to provide some uniform methods some uniform methods independent of a specific independent of a specific application for accessing the application for accessing the information that is stored.information that is stored.

Does not implements OOPs Does not implements OOPs concepts.concepts.

RDBMS (Relational Data RDBMS (Relational Data Base Management System) Base Management System) adds the additional adds the additional condition that the system condition that the system supports a tabular structure supports a tabular structure for the data, with enforced for the data, with enforced relationships between the relationships between the tables.tables.

Implements OOPs conceptsImplements OOPs concepts

Data IndependenceData Independence

Data Independence refers to the Data Independence refers to the immunity of user applications to make immunity of user applications to make changes in the definition and organization changes in the definition and organization of data.of data.

The data independence and operation The data independence and operation independence together gives the feature independence together gives the feature of data abstraction. There are two levels of data abstraction. There are two levels of data independenceof data independence

a)a) Logical / Conceptual data independence.Logical / Conceptual data independence.

b)b) Physical data independencePhysical data independence

Logical data independenceLogical data independence states states that if changes are done in application that if changes are done in application software and physical structure of software and physical structure of database changes need not to be done in database changes need not to be done in conceptual structure.conceptual structure.

Physical data independencePhysical data independence states states that if changes are done in application that if changes are done in application software and logical structure of software and logical structure of database changes need not to be done in database changes need not to be done in physical structure.physical structure.