The CDS Database

· Directory entries

A directory entry consists of a name and its attributes. One example is the name of an application server, whose attributes include the interface it exports and its location on the network.

· Directories

A CDS directory is a logical grouping of CDS information - it is a collection of directory entries. The directory is the administrative unit for replication. There can be one or more copies, or replicas, of a given directory. CDS directories are in a hierarchical relationship to one another; each directory has a parent directory, and may also have child directories.

· Clearinghouses

A clearinghouse is a physical CDS database - it is a collection of directory replicas. The clearinghouse is the database on a CDS server machine that the CDS server accesses in order to respond to its requests.

As an example of how the different types of CDS data elements relate to one another, imagine a directory P, which contains all the information about the printers in a given cell. This directory contains one directory entry per printer. The administrator of the cell may decide that the information contained in the Pdirectory is important enough that it needs to be replicated on more than one CDS server, so if one server goes down, the P information can still be found on the other server. To that end, replicas of the P directory might be kept in two clearinghouses - one replica in Clearinghouse A, and the other in Clearinghouse B.