DBMS

1. DBMS By Narinder Singh Computer Sc. Deptt

2. Topics • What is DBMS • File System Approach: its limitations • Why we need DBMS? • Difference between DBMS and Programming Languages • Difference between DBMS and RDBMS • Data Independence

3. DBMS • Database is collection of related Files. • Database is organizing data into tabular form i.e. in the form of rows and columns. • A Database Management System (DBMS) is a set of computer programs that controls the creation, maintenance, and the use of a database. • It allows organizations to place control of database development by database administrators (DBAs) and other specialists. • A DBMS is a system software package that helps the use of integrated collection of data records and files. • It allows different user application programs to easily access the same database.

4. File System Approach • Storing the data into a single file that is not linking with other file is the traditional file system approach. • All the records resides in a single file leads to the problems such as data redundancy, inconsistency etc.

5. Limitations of File System Approach • Separation and isolation of data-Difficult to access data that is available (eg. from two files – Student that achieved good academic result and active in extra curriculum activities) • Duplication of data-Cost time and money to enter data more than once-Additional storage space is needed - cost-Inconsistencies of data • Data dependence-File structure is defined in the program code.-Changes to an existing structure are difficult to make • Incompatible file formats-Programs are written in different languages, and so cannot easily access each other’s files. • Fixed Queries/Proliferation of application programs-Programs are written to satisfy particular functions.-Any new requirement needs a new program.

6. Advantages of DBMS • Controlling redundancy • Providing storage structure for efficient query processing. • Restricting unauthorized users. • Providing concurrency. • Providing backup and recovery. • Enforcing integrity constraints. • Improved data sharing.

7. Disadvantages of RBMS • Centralization: That is use of the same program at a time by many user sometimes lead to loss of some data. • High cost of software. • Technical expertise are required.

8. DBA • Database Administrator (DBA) is the person(s) , who manages the database. • Functions of DBA includes • Creation of database. • Decide Storage for the database. • Responsible for backup and recovery. • Create new users and assign privileges to them.

9. DBMS has to be persistent, that is it should be accessible when the program created the data. A DBMS also has to provide some uniform methods independent of a specific application for accessing the information that is stored. Does not implements OOPs concepts. RDBMS (Relational Data Base Management System) adds the additional condition that the system supports a tabular structure for the data, with enforced relationships between the tables. Implements OOPs concepts DBMS vs RDBMS

10. Data Independence • Data Independence refers to the immunity of user applications to make changes in the definition and organization of data. • The data independence and operation independence together gives the feature of data abstraction. There are two levels of data independence • Logical / Conceptual data independence. • Physical data independence

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