FIT2100 Lecture Notes - Lecture 11: Unique Key, Indexed File, Inode
31 May 2018
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Lecture 11
File Management
Files:
-Data collections created by users, with desirable properties or attributes
-Long-term existence: file are stored on disk or other secondary storage and do not disappear
when a user logs off
-Sharable between processes: files have names and can have associated access permissions that
permit controlled sharing
-Structure: files can be organised into hierarchical or more complex structure to reflect the
relationships among files
File Systems:
-Provide a means to store data organised as files as well as a collection of functions that can be
performed on files
-Maintain a set of attributes associated with the file
-Typical operations include: create, delete, open, close, read, write
File Structure:
-Four terms are commonly used when discussing files
-Field
-Basic element of data
-Contains a single value
-Fixed or variable length
-Record
-Collection of related fields — treated as a unit by some application program
-Fixed or variable length
-File
-Collection of similar records
-Treated as a single entity
-May be referenced by name
-Access control restrictions usually apply at the file level
-Database
-Collection of related data
-Relationships among elements of data are explicit
-Designed for use by a number of different applications
-Consists of one or more types of files
File Management System: Objectives
-Meet the data management needs and requirements of the users
-Guarantee that the data in the file are valid
-Optimise system performance
-Provide I/O support for a variety of storage device types
-Provide a standardised set of I/O interface routines to user processes
-Provide I/O support for multiple users in the case of multiple-user systems
-Minimise the potential for lost or destroyed data
File Organisation & Access
-File organisation is the logical structuring of the records as determined by the way in which they
are accessed
-In choosing a file organisation, several criteria are important
-Short access time
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Document Summary
Data collections created by users, with desirable properties or attributes. Long-term existence: file are stored on disk or other secondary storage and do not disappear when a user logs off. Sharable between processes: files have names and can have associated access permissions that permit controlled sharing. Structure: files can be organised into hierarchical or more complex structure to reflect the relationships among files. Provide a means to store data organised as files as well as a collection of functions that can be performed on files. Maintain a set of attributes associated with the file. Typical operations include: create, delete, open, close, read, write. Four terms are commonly used when discussing files. Collection of related fields treated as a unit by some application program. Access control restrictions usually apply at the file level. Relationships among elements of data are explicit. Designed for use by a number of different applications. Consists of one or more types of files.
