A client/server system is a distributed systems in which,

(a) some sites are client sites and others are serer sites

(b) all data resides at the server sites

(c) all applications execute at the client sites

The term ‘client/server’ refers primarily to an architecture, or logical division of responsibilities , the client is the application (also known as the frontend), and the server is the DBMS (also known as the backend).

A client/server system can be thought of as a distributed system in which all requests originate at one site and all processing is performed at another. In practice the client site might well have its own local databases, but those databases will not play a direct part in the client/server arrangement as such.

Client/Server provides a low-priced robust solution to user requirements. This approach permits downsizing production subsystem while allowing the clients and servers the necessary tools and facilitate to control, manage and tune the environment in which they operate.

Most client/server solution are also very attentive in matters of security. Access to any resources can be defines to the file level, with such access being controlled through identification and authorization. Logically defined closed use groups can be setup to enable the enhancing of security measures by network administrations.

It allows the database management including security, performance, backup, server enforced integrity to be part of the database machine avoiding the requirement to write large number of redundant piece of code dealing with database field validation and referential integrity.

The successful organizations have to be marked drives and competitive in the times to come, and they will use Client/Server computing as the enabling technology to add values to their business. Powerful workstations will be available to all end users to be used as clients to access the information on the servers which are distributed globally. The networks of the future will support much higher bandwidth by using technologies like corporate networks will cut across the boundaries of cities or even countries and they will be connected to major networks around the worlds.

E-R DIAGRAM :

E-R Diagram constitute a technique for representing the logical structure of a database in a pictorial manner. This analysis is then used to organize data as a relation, normalising relation and finally obtaining a relation database.

Entities : Which specify distinct real-world items in an application.

Properties (or): Which specify properties of an entity and relationships.

Attributes

Relationships : Which connect entities and represent meaningful dependencies between them.

The basic objective of normalization is to be reduce redundancy which means that information is to be stored only once. Storing information several times leads to wastage of storage space and increase in the total size of the data stored.

If a Database is not properly designed it can gives rise to modification anomalies. Modification anomalies arise when data is added to, changed or deleted from a database table. Similarly, in traditional databases as well as improperly designed relational databases, data redundancy can be a problem. These can be eliminated by normalizing a database.

Normalization is the process of breaking down a table into smaller tables. So that each table deals with a single theme. There are three different kinds of modifications of anomalies and formulated the first, second and third normal forms (3NF) is considered sufficient for most practical purposes. It should be considered only after a through analysis and complete understanding of its implications.

This form also called as a “flat file”. Each column should contain data in respect of a single attributes and no two rows may be identical.

To bring a table to First Normal Form, repeating groups of fields should be identified and moved to another table.

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