tailieunhanh - Ebook Fundamentals of database systems (6/E): Part 2

Part 2 book “Fundamentals of database systems” has contents: Indexing structures for files, algorithms for query processing and optimization, physical database design and tuning, concurrency control techniques, database recovery techniques, database security, distributed databases, distributed databases, and other contents. | part 7 File Structures, Indexing, and Hashing This page intentionally left blank chapter 17 Disk Storage, Basic File Structures, and Hashing D atabases are stored physically as files of records, which are typically stored on magnetic disks. This chapter and the next deal with the organization of databases in storage and the techniques for accessing them efficiently using various algorithms, some of which require auxiliary data structures called indexes. These structures are often referred to as physical database file structures, and are at the physical level of the threeschema architecture described in Chapter 2. We start in Section by introducing the concepts of computer storage hierarchies and how they are used in database systems. Section is devoted to a description of magnetic disk storage devices and their characteristics, and we also briefly describe magnetic tape storage devices. After discussing different storage technologies, we turn our attention to the methods for physically organizing data on disks. Section covers the technique of double buffering, which is used to speed retrieval of multiple disk blocks. In Section we discuss various ways of formatting and storing file records on disk. Section discusses the various types of operations that are typically applied to file records. We present three primary methods for organizing file records on disk: unordered records, in Section ; ordered records, in Section ; and hashed records, in Section . Section briefly introduces files of mixed records and other primary methods for organizing records, such as B-trees. These are particularly relevant for storage of object-oriented databases, which we discussed in Chapter 11. Section describes RAID (Redundant Arrays of Inexpensive (or Independent) Disks)—a data storage system architecture that is commonly used in large organizations for better reliability and performance. Finally, in Section we describe .