Databases Reference
In-Depth Information
database server. This server and the database it hosts contain all of the business
data. This model is relatively easy to implement, but can become difficult to sup-
port if you have to provide data access for remote users.
The
distributed model
uses multiple database servers with the data spread
across the servers. Each server typically contains its own unique set of data.
Servers are usually deployed in different physical locations. The database servers
can all use the same DBMS, or use different database products, giving you a
heterogeneous data environment
made of mixed database types, operating sys-
tems, and hardware platforms. Potential drawbacks include the need for reliable
communication between the database servers and the fact that different database
products don't always interface well with each other.
SELF-CHECK
•
Explain basic database concepts relating to data and transactions.
•
Discuss how the basic building blocks of a database work together
to provide a data environment.
•
List business factors that would determine whether it would be
better to deploy a centralized or distributed database model. Be
sure to include cost as part of the determining factors.
•
Compare the role of the data repository with that of the data dictio-
nary and describe how the two interact.
2.2 Understanding Basic Database Models
The basic database models are:
▲
Hierarchical database model
▲
Network database model
▲
Relational database model
▲
Object-oriented database model
The original implementations of the hierarchical and network approaches to
database are both called navigational approaches because of the way that pro-
grams have to “navigate” through hierarchies and networks of data to find the
data they need. Both of these technologies were developed in the 1960s and,
relative to the other approaches, are somewhat similar in structure.
Our focus is on
relational databases,
which are databases based on the rela-
tional model, and hybrid databases, which are based on an integration of different
