In computing, a file system (often also written as filesystem) is a method for storing and organizing computer files and the data they contain to make it easy to find and access them. File systems may use a data storage device such as a hard disk or CD-ROM and involve maintaining the physical location of the files, they might provide access to data on a file server by acting as clients for a network protocol (e.g., NFS, SMB, or 9P clients), or they may be virtual and exist only as an access method for virtual data (e.g., procfs).
More formally, a file system is a set of abstract data types that are implemented for the storage, hierarchical organization, manipulation, navigation, access, and retrieval of data. File systems share much in common with database technology, but it is debatable whether a file system can be classified
Also known as on-disk structure, is the file system used by Hewlett-Packard's OpenVMS operating system, and also (in a simpler form) by the older RSX-11. It is a hierarchical file system, with support for access control lists, record-oriented I/O, remote network access, and file versioning.
Files-11 is similar to, but significantly more advanced than, the filesystems used in previous Digital Equipment Corporation operating systems
native OpenVMS file system is descended from older DEC operating systems, and is similar in many ways. A major difference is the layout of directories. These file systems all provided some form of rudimentary non-hierarchical directory structure, typically based on assigning one directory per user account. Under RSTS/E, each user account was represented by two numbers, a [project,programmer] pair, and had an associated directory. Special system files, such as program executables and the OS itself, were stored in the directory of a reserved system account.
While this was suitable for PDP-11 systems, which possessed limited permanent storage capacity, the advent of VAX systems with very large hard drives (for the time) required a more flexible method of file storage—hierarchical directory layout in particular, the most notable improvement in ODS-2.
Extensive use is made of the system of disk and tape handling originally developed within the ATMOL [36] program system, with the various files of integral data output to one or more direct access data sets. Such data sets are allocated to the program using logical file names (LFNs) in the range ED0, ED1, ..., ED19 and MT0, MT1, ..., MT19. In Table 1 we list those files used by the program, and define the default LFN associated with each file. A full description of data set management will not be given here: for the present it suffices to note the following;
The Dumpfile, which in default is routed to ED3, is crucial to the program and controls all restart activities, This file is organised into variable length sections, with the user nominating various sections for data storage e.g., eigenvectors. The sections are characterised by integers (in the range 1 - 350), which are specified by the user through data input.
The Scratchfile, which is routed to ED7, is used in all runs of the program as a file for house-keeping activities. While this data set need never be maintained across separate runs of the program, the user should be aware of the role of ED7 and avoid any attempts to use the data set in, for example, the re-routing of integral output.
Each data file is block addressable (1 block = 512 words). In default output of each file commences at block 1 of the associated data set, and continues in uninterrupted fashion until output is complete. With certain exceptions, the user may control file usage in several ways;
redefine the LFN to be associated with a given data file
redefine the starting block for the file, allowing several files of data to be stored on the same data set
partition output of a given file over several data sets, specifying the associated LFNs, and the starting and terminal blocks of each LFN. Th
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