Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. The DCE Distributed File System (DCE/DFS) is the remote file access protocol used with the Distributed Computing Environment. It was based on the AFS Version 3.0 protocol that was developed commercially by Transarc Corporation. AFS Version 3.0 was in turn based on the Andrew File System Version 2.0 protocol (also used by the Coda disconnected file system) originally developed at Carnegie Mellon University. DCE/DFS consisted of multiple cooperative components that provided a network file system with strong file system semantics, attempting to mimic the behavior of POSIX local file systems while taking advantage of performance optimizations when possible. A DCE/DFS client system utilized a locally managed cache that would contain copies (or regions) of the original file. The client system would coordinate with a server system where the original copy of the file was stored to ensure that multiple clients accessing the same file would re-fetch a cached copy of the file data when the original file had changed.