Type of Accesses in Distributed Database - DDBMS


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.

Application Requires Remote Data:

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.

Application Requires Execution of Auxiliary Program at Remote Site