Editing Distributed Computing Environment (section)

==Architecture==

DCE is intended to support [[high availability]] systems: when a server does not respond (because of server failure or communications failure), clients can be constructed to automatically use a replica of that server instead.<ref name="change" />{{rp|11}}{{rp|21}}

The largest unit of management in DCE is a ''cell''. The highest privileges within a cell are assigned to a role called ''cell administrator'', normally assigned to the "user" ''cell_admin''. Multiple cells can be configured to communicate and share resources with each other. All principals from external cells are treated as "foreign" users and privileges can be awarded or removed accordingly. In addition to this, specific users or groups can be assigned privileges on any DCE resource, something which is not possible with the traditional UNIX filesystem, which lacks ACL's.

Major components of DCE within every cell are:
#The Security Server that is responsible for authentication
#The Cell Directory Server (CDS) that is the repository of resources and ACLs and
#The Distributed Time Server that provides an accurate clock for proper functioning of the entire cell

Modern DCE implementations such as IBM's are fully capable of interoperating with Kerberos as the security server, LDAP for the CDS and the [[Network Time Protocol]] implementations for the time server.

DCE/DFS is a DCE-based application which provides a distributed filesystem on DCE. DCE/DFS can support replicas of a fileset (the DCE/DFS equivalent of a filesystem) on multiple DFS servers - there is one read-write copy and zero or more read only copies. Replication is supported between the read-write and the read-only copies. In addition, DCE/DFS also supports what are called "backup" filesets, which if defined for a fileset are capable of storing a version of the fileset as it was prior to the last replication.

DCE/DFS is believed to be the world's only distributed filesystem that correctly implements the full POSIX filesystem semantics, including byte range locking.<ref name="advogato" />

DCE/DFS was sufficiently reliable and stable to be utilised by [[IBM]] to run the back-end filesystem for the 1996 [[Olympics]] web site, seamlessly and automatically distributed and edited worldwide in different time zones.<ref name="advogato" />