The access to a remote database by an application can be performed in one of two basic ways, as shown in figures below.
1) Application Requires Remote Data:
the application issues a database access request which refers remote data. This request is automatically routed by the DDBMS to the site where the data is located; then it is executed at that site, and the result is returned. In this way, the basic units which are shipped between systems are the database access primitive & the result obtains by executing this primitive. If this approach is used for remote access, distribution transparency can be implemented by providing global filenames; the primitives could then be automatically addressed to the appropriate remote sites.
1)
Application Requires Execution of
Auxiliary Program at Remote Site:
shows a different approach, in which the. This auxiliary
program, written by the application programmer, accesses the remote database
and returns the result to the requesting application.
