(Melanie)Some databases are distributed among multiple geographical locations; a logically related database that is stored in two or more physically independent sites is called a distributed database. (Coronel.) It is desirable to hide the inherent complexities of a database with a geographical spread from the end user, presenting the end user instead with the sense of working with a centralized database, which is somewhat ironically called transparency. Distribution transparency allows a physically dispersed database to be managed as though it were a centralized database.
Distribution transparency affects the way end users and programmers interact with a database. (Coronel.) There are three recognized levels of distribution transparency (fragmentation, location, and local mapping transparencies) which all require different levels of specification from the end user or programmers seeking to access information. Fragmentation transparency is the highest level of distribution transparency, in which the end user or programmer does not need to know the database is partitioned, and therefore neither fragment names nor fragment locations are specified prior to data access. When trying to locate information in a distributed database with fragmentation transparency, the user need only enter the same simple query they would use in a centralized database. If a company was in multiple cities, or even global, with its database distributed across all its offices, the user could simply search the entire database without specificity.
Location transparency requires the user to know the name of the database fragments, but they need not specify where those fragments are stored. (Coronel.) With location transparency, instead of a generalized query, the user needs to specifically search for the fragments by name.
The lowest level of transparency is local mapping transparency, which requires the user to specify both the fragment names and their locations. (Coronel.) Local mapping is considered the lowest level of transparency because the geographic barriers between the fragments are most noticeable and thus least transparent. Location mapping transparency is a more difficult and time-consuming query for the user as the user must know and specify the most information. (Transparencies.) Requiring the most information, however, can offer the most security for the information stored in the database.
References:
Coronel, C., & Morris, S. (2019). Database systems: Design, implementation, and management (13th e). Cengage Learning.
Transparencies in ddbms. (2021, June 10). GeeksforGeeks. https://www.geeksforgeeks.org/transparencies-in-ddbms/
