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18 Cards in this Set
- Front
- Back
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In a file system, what is a 'field'?
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Smallest logical item of data understood by the file system.
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Give two examples of a field.
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Integer, string
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In a file system, what is a 'record'?
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One or more fields but treated as a single unit by applications for read/write purposes.
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In a file system, what is a 'file'?
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Collection of identically represented records, accessed by unique names.
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In a file system, what is a 'database'?
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One or more files, whose contents are logically related.
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What is DBMS?
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Database Management System. Manages a whole drive or partition, assuming the role of OS in access, security and backup.
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What are the goals of a file management system?
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To support the storage, searching and modification of user data, to optimise throughput and response time and to provide transparent access to devices
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How does a file management system meet the needs of multiple users?
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Recording of owners, file names, permissions
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With what do device drivers directly communicate?
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IO hardware, commencing requests and receiving completion notification via DMA
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What is the role of the IO Supervisor?
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To manage choice of device, its status and to allocate IO buffers
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Who really 'owns' directories?
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The OS - deleting a file within a directory leaves the OS to deallocate disk blocks
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What is an Inode?
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An information structure kept separate in modern OS from its directory entry.
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What information is stored within an inode?
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File type, size and limit, owner, users, access constraints, dates and times of accesss, creation, modification and backup/recovery
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What is the problem with contiguous allocation of files in blocks?
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Requires that the maximum size of the file be determined upon creation and hence cannot grow. We see internal and external fragmentation if files are a bad fit and as files are deleted.
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What is the opposite of contiguous allocation of files?
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Chained allocation
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WHat is chained allocation?
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Chained blocks which form a linked list, where each block contains a 32-bit pointer indicating the address of the next file in the chain
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What is the benefit of chained allocation?
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Can place new blocks anywhere on the disk as they needn't be contiguous.
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What is the indexed allocation method?
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Multi-level index for each file.
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