Databases Reference
In-Depth Information
Figure 5-1
Inputs Into the Physical Database Design Process
• The Tables Produced by the Logical Database Design
Process
• Business Environment Requirements
Response Time Requirements
Throughput Requirements
• Data Characteristics
Data Volume Assessment
Data Volatility
• Application Characteristics
Application Data Requirements
Application Priorities
• Operational Requirements
Data Security Concerns
Backup and Recovery Concerns
• Hardware and Software Characteristics
DBMS Characteristics
Hardware Characteristics
Inputs to the physical design.
Figure 5-1 lists the inputs to physical database design, which are also fac-
tors important to the design process. These inputs fall into several subgroups.
We'll take a look at each of these physical design inputs and factors, one-by-one.
The tables produced by the logical database design process (which for sim-
plicity we will now refer to as the logical design) form the starting point of the
physical database design process. These tables reflect all of the data in the busi-
ness environment. In theory, they have no data redundancy (or at least minimal
redundancy), and they have all of the foreign keys in place that are needed to
establish the relationships in the business environment.
This does not necessarily reflect an optimum performance environment. Keep
in mind that at this point, we have limited our design to database tables only. We
still need to design the objects, like indexes, that will help to optimize data access.
Even then, there may be additional performance issues. For example, it is possi-
ble that a particular query may require the joining of several tables, which may
cause an unacceptably slow response from the database. Clearly then, these tables,
in their current form, might be unacceptable from a performance point of view.
This is why we need to make additional modifications and physical design changes.
One important point is that none of these factors operates in a vacuum. Each
influences the others. Actions taken to help you meet the needs of one require-
ment better could actually make it harder to meet another set of requirements.
