The ability to access remote (or external) tables as if they were local is a hallmark of Component Integration Services. Component Integration Services presents tables to a client application as if all the data in the tables were stored locally. Remote tables are mapped to local proxy tables which hold metadata. Internally, when a query involving remote tables is executed, the storage location is determined, and the remote location is accessed so that data can be retrieved.
The access method used to retrieve remote data is determined by two attributes of the external object:
The server class associated with the remote object
The object type
To achieve location transparency, tables must first be mapped to their corresponding external locations.