Chapter 12 - M12_STAL6329_06_SE_C12.QXD 2/21/08 9:40 PM...

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F ILE M ANAGEMENT 12.1 Overview Files and File systems File Structure File Management Systems 12.2 File Organization and Access The Pile The Sequential File The Indexed Sequential File The Indexed File The Direct or Hashed File 12.3 File Directories Contents Structure Naming 12.4 File Sharing Access Rights Simultaneous Access 12.5 Record Blocking 12.6 Secondary Storage Management File Allocation Free Space Management Volumes Reliability 12.7 File System Security 12.8 UNIX File Management Inodes File Allocation Directories Volume Structure Traditional UNIX File Access Control Access Control Lists in UNIX 12.9 LINUX Virtual File System The Superblock Object The Inode Object The Dentry Object The File Object 12.10 Windows File System Key Features of NTFS NTFS Volume and File Structure Recoverability 12.11 Summary 12.12 Recommended Reading 12.13 Key Terms, Review Questions, and Problems 551 CHAPTER M12_STAL6329_06_SE_C12.QXD 2/21/08 9:40 PM Page 551
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552 CHAPTER 12 / FILE MANAGEMENT In most applications, the file is the central element.With the exception of real-time ap- plications and some other specialized applications, the input to the application is by means of a file, and in virtually all applications, output is saved in a file for long-term storage and for later access by the user and by other programs. Files have a life outside of any individual application that uses them for input and/or output. Users wish to be able to access files, save them, and maintain the in- tegrity of their contents.To aid in these objectives, virtually all operating systems pro- vide file management systems. Typically, a file management system consists of system utility programs that run as privileged applications. However, at the very least, a file management system needs special services from the operating system; at the most, the entire file management system is considered part of the operating system.Thus,it is ap- propriate to consider the basic elements of file management in this book. We begin with an overview, followed by a look at various file organization schemes.Although file organization is generally beyond the scope of the operating sys- tem, it is essential to have a general understanding of the common alternatives to ap- preciate some of the design tradeoffs involved in file management. The remainder of this chapter looks at other topics in file management. 12.1 OVERVIEW Files and File Systems From the user’s point of view, one of the most important parts of an operating sys- tem is the file system.The file system provides the resource abstractions typically as- sociated with secondary storage. The file system permits users to create data collections, called files, with desirable properties, such as Long-term existence: Files are stored on disk or other secondary storage and do not disappear when a user logs off.
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Chapter 12 - M12_STAL6329_06_SE_C12.QXD 2/21/08 9:40 PM...

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