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Consistency Semantics

_ Important criterion for evaluation of file systems that allows file sharing

_ Specifies the semantics of multiple users accessing a file simultaneously

_ Specifies when modifications of data by one user are observable by others

_ File session

·        Series of accesses between an open and close operation by the same user on the same file

_ Unix Semantics

·        Writes to an open file by a user are visible immediately to other users that have this file open at the same time

·        There is a mode of sharing where users share the pointer of current location into the file. Advancing of pointer

          by one user affects all sharing users. A file has single image that interleaves all accesses, regardless of their origin