Database Management System

Prepared by Mrs. N.Kalaivani MCA., M.Phil, SET Assosiate Professor Department of Kongunadu Arts & Science College (Autonomous) Coimbatore-29. Management System

Database Management System (DBMS): It is a collection of programs that enables to create and maintain a database. In other words it is general-purpose software that provides the users with the processes of defining, constructing and manipulating the database for various applications. DBMS Languages

Database languages are used to read, update and store data in a database. There are several such languages that can be used for this purpose; one of them is SQL (Structured ). Types of DBMS languages

 Data Manipulation Language  Data Control Language  Transaction Control Language 1. Data Definition Language (DDL) DDL is used for specifying the . It is used for creating tables, schema, indexes, constraints etc. in database.  To create the database instance – CREATE  To alter the structure of database – ALTER  To drop database instances – DROP  To delete tables in a database instance – TRUNCATE  To rename database instances – RENAME  To drop objects from database such as tables – DROP  To Comment – Comment  All of these commands either defines or update the database schema that’s why they come under Data Definition language. 2. Data Manipulation Language (DML)

DML is used for accessing and manipulating data in a database. The following operations on database comes under DML:  To read records from (s) – SELECT  To insert record(s) into the table(s) – INSERT  Update the data in table(s) – UPDATE  Delete all the records from the table – DELETE 3. Data Control language (DCL)

 DCL is used for granting and revoking user access on a database –  To grant access to user – GRANT  To revoke access from user – REVOKE 4. Transaction Control Language(TCL)

 The changes in the database that we made using DML commands are either performed or rollbacked using TCL.  To persist the changes made by DML commands in database – COMMIT  To rollback the changes made to the database – ROLLBACK

 A Database Administrator, Database Analyst or Database Developer is the person responsible for managing the information within an organization.  The overall goal of the DBA is to keep the server up at all times and to provide users with access to the required information when they need it. The DBA makes sure that the database is protected and that any chance of data loss is minimized. DBA Responsibilities

1. Design of the conceptual and physical schemas: The DBA is responsible for interacting with the users of the system to understand what data is to be stored in the DBMS and how it is likely to be used. The DBA creates the original schema by writing a set of definitions and is Permanently stored in the ''. 2. Security and Authorization: The DBA is responsible for ensuring the unauthorized data access is not permitted. The granting of different types of authorization allows the DBA to regulate which parts of the database various users can access. 4. Storage structure and Access method definition: The DBA creates appropriate storage structures and access methods by writing a set of definitions, which are translated by the DDL compiler. 5. Data Availability and Recovery from Failures: The DBA must take steps to ensure that if the system fails, users can continue to access as much of the uncorrupted data as possible. The DBA also work to restore the data to consistent state. 4. : The DBA is responsible for modifying the database to ensure adequate Performance as requirements change. 5. Integrity Constraint Specification: The integrity constraints are kept in a special system structure that is consulted by the DBA whenever an update takes place in the system. The DBA should posses the following skills (1) A good knowledge of the . (2) A good knowledge of physical (3) Ability to perform both Oracle and also operating system performance monitoring and the necessary adjustments. (4) Be able to provide a strategic database direction for the organization. (5) Excellent knowledge of Oracle and recovery scenarios. (6) Good skills in all Oracle tools. (7) A good knowledge of Oracle security management. (8) A good knowledge of how Oracle acquires and manages resources. (9) Sound knowledge of the applications at your site. (10) Experience and knowledge in migrating code, database changes, data and