A DCM cluster is any group of DCM databases that shares data. Each database in a cluster is manually given a unique database ID (dbid). database IDs are used to define source and destination databases. They are also used to make each object version in the cluster unique. For example, DCM assigns the Irvine database ID to a main.c object created in the irvine database. This ID makes the object different from a main.c object created in the san_jose database.