Beginning Oracle Database 11g Administration From Novice to Professional

CHAPTER 7
Physical Database Design
In most people’s vocabularies, design means veneer. It’s interior decorating. It’s the
fabric of the curtains and the sofa. But to me, nothing could be further from the
meaning of design. Design is the fundamental soul of a man- made creation that
ends up expressing itself in successive outer layers of the product or service.
—Apple CEO Steve Jobs, interviewed in Fortune magazine; January 24, 2000
The two stages of database design are logical and physical design. Logical database
design, also referred to as data modeling, is done first. It is the process of studying the
workings of a business organization, constructing a set of tables to store the business data,
and understanding the constraints on the data, the dependencies between the tables, and
the business rules concerning the data. The logical database design process is conducted
without reference to any specific database technology such as Oracle or Microsoft SQL
Server, and a simple example can be found in Oracle Database 11g Java Developer’s Guide.
Tools such as Oracle Designer, CA ERwin Data Modeler, Embarcadero ER/Studio, and
Toad Data Modeler can be used for the purpose. Physical database design follows logical
database design. First, the logical model is mapped to the proprietary features of the
chosen database technology. Security requirements, integrity requirements, and business
rules are also implemented. Finally, we consider performance: the ability of the database
engine to handle work requests efficiently. This typically involves the creation of indexes
on the data, and Oracle Database provides a wealth of indexing mechanisms to choose
from.
Performance considerations can come to the forefront at any time during the life of
the database; new queries can be introduced at any time. Database administrators must
therefore understand the mechanisms that can be used to improve performance.
Three broad categories of performance mechanisms are available for physical database
design. Indexes can be used to quickly find the data. Partitions and clusters can be used to
organize the data. Finally, materialized views and denormalized tables can be used to perform
expensive operations like Joins ahead of time.
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