Refining the Database Design › Evaluating the Database Design

Evaluating the Database Design

You have created a preliminary model for a physical database and have identified the entities in the database. You have also gathered the information necessary to refine this diagram and have assigned location modes to the entities. Now you will refine the preliminary design to allow for optimal transaction and system performance.

Evaluation considerations

Before you refine the data structure diagram, you need to evaluate the design for performance. To satisfy performance requirements for each individual business transaction, you need to consider the following issues:

• Input/output (I/O) performance—Is the number of I/O operations performed against the database sufficiently low to provide satisfactory transaction performance?
• CPU time—Does the structure of the physical database optimize the use of CPU processing?
• Space management—Do design choices help to conserve storage resources?

Once you have refined the database to satisfy each individual transaction, you need to determine how the system will be affected by the concurrent execution of several transactions. To avoid excessive contention for database resources, you need to make appropriate changes to the physical model.

Refining the database design

Like many other database design procedures, refining the database design is an iterative process, as shown below. As you refine the design, you need to evaluate the design for performance. When you make changes, you should review the design to ensure that it will optimize processing for all critical transactions and also minimize the likelihood of contention.