Database Users and Administrators

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A primary goal of a database system is to retrieve information from and store
new information into the database. People who work with a database can be
categorized as database users or database administrators.

1. Database Users and User Interfaces

There are four different types of database-system users, differentiated by the way
they expect to interact with the system. Different types of user interfaces have
been designed for the different types of users.

Na¨?ve users are unsophisticated users who interact with the system by invoking
one of the application programs that have been written previously.
For example, a clerk in the university who needs to add a new instructor to
department A invokes a program called new hire. This program asks the clerk
for the name of the new instructor, her new ID, the name of the department
(that is, A), and the salary.

    The typical user interface for na¨?ve users is a forms interface, where the
user can fill in appropriate fields of the form. Na¨?ve users may also simply
read reports generated from the database.

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     As another example, consider a student, who during class registration
period, wishes to register for a class by using a Web interface. Such a user
connects to a Web application program that runs at a Web server. The application
first verifies the identity of the user, and allows her to access a form
where she enters the desired information. The form information is sent back
to the Web application at the server, which then determines if there is room
in the class (by retrieving information from the database) and if so adds the
student information to the class roster in the database.

Application programmers are computer professionalswho write application
programs. Application programmers can choose frommany tools to develop
user interfaces. Rapid application development (RAD) tools are tools that enable
an application programmer to construct forms and reportswith minimal
programming effort.

Sophisticated users interact with the system without writing programs. Instead,
they form their requests either using a database query language or by
using tools such as data analysis software. Analysts who submit queries to
explore data in the database fall in this category.

Specialized users are sophisticated users who write specialized database
applications that do not fit into the traditional data-processing framework.
Among these applications are computer-aided design systems, knowledgebase
and expert systems, systems that store data with complex data types (for
example, graphics data and audio data), and environment-modeling systems.

2.  Database Administrator

One of the main reasons for using DBMSs is tohave central control of both thedata
and the programs that access those data. A person who has such central control
over the system is called a database administrator (DBA). The functions of a DBA

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• Schema definition. The DBA creates the original database schema by executing
a set of data definition statements in the DDL.

• Storage structure and access-method definition.

• Schema and physical-organization modification. TheDBAcarries out changes
to the schema and physical organization to reflect the changing needs of the
organization, or to alter the physical organization to improve performance.

• Granting of authorization for data access. By granting different types of
authorization, the database administrator can regulate which parts of the
database various users can access. The authorization information is kept in a
special system structure that the database system consults whenever someone
attempts to access the data in the system.

• Routine maintenance. Examples of the database administrator’s routine
maintenance activities are:

? Periodically backing up the database, either onto tapes or onto remote
servers, to prevent loss of data in case of disasters such as flooding.

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? Ensuring that enough free disk space is available for normal operations,
and upgrading disk space as required.

? Monitoring jobs running on the database and ensuring that performance
is not degraded by very expensive tasks submitted by some users.

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