The types of users and their roles and responsibilities at a site can vary. A small site can have one database administrator who administers the database for application developers and users. A very large site can find it necessary to divide the duties of a database administrator among several people.
There are following types of users:

1.    Database Administrators
2.    Security Officers
3.    Network Administrators
4.    Application Developers
5.    Application Administrators
6.    Database Users

Database Administrators:

Each database requires at least one database administrator (DBA) to administer it. Because an Oracle database system can be large and can have many users, often this is not a one person job. In such cases, there is a group of DBAs who share responsibility.

A database administrator’s responsibilities can include the following tasks:
-    Installing and upgrading the Oracle server and application tools
-    Allocating system storage and planning future storage requirements for the database system
-    Creating primary database storage structures (table spaces) after application developers have designed an application
-    Creating primary objects (tables, views, indexes) once application developers have designed an application
-    Modifying the database structure, as necessary, from information given by application developers
-    Enrolling users and maintaining system security
-    Controlling and monitoring user access to the database
-    Monitoring and optimizing the performance of the database
-    Planning for backup and recovery of database information
-    Maintaining archived data on tape
-    Backing up and restoring the database

Security Officers:

A security officer enrolls users, controls and monitors user access to the database, and maintains system security.

Network Administrators:

A network administrator can administer Oracle networking products, such as Oracle Net.

Application Developers:

Application developers design and implement database applications. Their responsibilities include the following tasks:

-    Designing and developing the database application
-    Designing the database structure for an application
-    Estimating storage requirements for an application
-    Specifying modifications of the database structure for an application
-    Relaying the above information to a database administrator
-    Tuning the application during development
-    Establishing an application’s security measures during development

Application Administrators:

Application administrators administrate a particular application. Each application can have its own administrator.

Database Users:

Database users interact with the database through applications or utilities. A typical user’s responsibilities include the following tasks:

-    Entering, modifying, and deleting data, where permitted
-    Generating reports from the data