Fundamentals of Database Management Systems, Second Edition

CHAPTER 8

PHYSICAL DATABASE DESIGN

If computers ran at infinitely fast speeds and data stored on disks could be found and brought into primary memory for processing literally instantly, then logical database design would be the only kind of database design to talk about. Well structured, redundancy-free third normal form tables are the ideal relational database structures and, in a world of infinite speeds, would be practical, too. But, as fast as computers have become, their speeds are certainly not infinite and the time necessary to find data stored on disks and bring it into primary memory for processing are crucial issues in whether an application runs as fast as it must. For example, if you telephone your insurance company to ask about a claim you filed and the customer service agent takes two minutes to find the relevant records in the company's information system, you might well become frustrated with the company and question its ability to handle your business competently. Data storage, retrieval, and processing speeds do matter. Regardless of how elegant an application and its database structures are, if the application runs so slowly that it is unacceptable in the business environment, it will be a failure. This chapter addresses how to take a well structured relational database design and modify it for improved performance.

OBJECTIVES

• Describe the principles of file organizations and access methods.
• Describe how disk storage devices work.
• Describe the concept of physical ...