Page 187 - DCAP312_WEB_TECHNOLOGIES_II

Unit 9: The Database Model

9.5 Types of Databases Notes

Through now you are influenced of the meaning of information for an association. You know
that information is a key business asset and that it has to be managed, protected, and used like
any other major asset. The corporate database that holds an organization’s data is the original
foundation for corporate information. Organizations are also faced with questions regarding
how and where to hold the corporate data.
Where should an enterprise hold its data? Should all the corporate data be kept centrally in
one place? If so, what are the advantages and disadvantages? What are the implications of this
arrangement?
Organizations primarily adopt one of two approaches. If the entire database is kept in one
centralized location, this type of database is a centralized database. On the other hand, if fragments
of the database are physically placed at various locations, this type of database is a distributed
database. Each type has its own benefits and shortcomings. Again, whether an enterprise adopts
a centralized or a distribute approach depends on the organizational setup and the information
requirements. Let us review the two types.

The corporate data should be divided into suitable fragments and the pieces
kept at different locations

9.5.1 Centralized Database
Figure 9.4 illustrates a central database. Personalized databases are always centralized in one
position. If your company has a centralized computer system, then the database must exist in
in that central location. In the client/server building, the database resides on a server machine.
The entire database may be kept on a single server machine and placed in a central location.
When all corporate data is in one place in a centralized database, companies find it easier to
manage and administer the database. You can control concurrent accesses to the same data in
the database easily in a centralized database. You can maintain security controls easily. However,
if your company’s operations are spread across remote locations, these locations must access
the centralized database through communication links. Here, data availability depends on the
capacity and dependability of the communication links.

Figure 9.4: Centralized Database

Enterprise
Database

All data at a single site. Common Examples:
Data access from remote sites Personal Database
through communication links.
Central Computer Database
Easy to administer.
Client/Server Database
Uncertain data availability.

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