Скачать или смотреть Chapter 12 Physical file organization and indexing

This chapter focuses on the most important principles pertaining to the physical organization of records and files. As such, it can be considered as the prerequisite to chapter 13, which applies these principles in the context of physical database organization. In this way chapter 12 and 13 are complementary in covering all facets of physical database design—the translation of a logical data model into an internal data model, including the design of indexes to speed up data access.
First, we present some overall properties of storage devices and the impact of the mechanicals of hard disk drives on the performance aspects of data retrieval. After that, we overview the mapping of logical modeling constructs onto physical concepts, and thus of the logical data model onto the internal model. Then, we briefly discuss record organization, covering the different alternatives to organize physical data records, consisting of individual data fields. After that comes the main body of this chapter, focusing on file organization and covering methods to organize records into physical files, as well as techniques to efficiently search for records with certain characteristics. We discuss several approaches, such as sequential files, hashing and the use of different index types, including B+-trees. Chapter 13 follows down from this chapter, applying the insights gained from the file organization section to the particular context of physical database organization.