Physical schema
Encyclopedia
Describes how data are to be represented and stored in secondary storage using a particular DBMS (e.g., Oracle).
Physical Schema is a term used in relation to data management.
Physical Schema describes the files and the indexes used to store the data in a DBMS.
In the ANSI
four-schema architecture, the internal schema was the view of data that involved data management technology. This was as opposed to the external schema that reflected the view of each person in the organization, or the conceptual schema
that was the integration of a set of external schemas. Subsequently the internal schema was recognized to have two parts:
The logical schema
was the way data were represented to conform to the constraints of a particular approach to database management. At that time the choices were hierarchical and network. Describing the logical schema, however, still did not describe how physically data would be stored on disk drives. That is the domain of the physical schema. Now logical schemas describe data in terms of relational tables and columns, object-oriented classes, and XML
tags. A single set of tables, for example can be implemented in dozens of different ways, up to and including the architecture where some rows are on a computer in Lagos
and others are on a computer in Warsaw
.
This is the physical schema.
Physical Schema is a term used in relation to data management.
Physical Schema describes the files and the indexes used to store the data in a DBMS.
In the ANSI
American National Standards Institute
The American National Standards Institute is a private non-profit organization that oversees the development of voluntary consensus standards for products, services, processes, systems, and personnel in the United States. The organization also coordinates U.S. standards with international...
four-schema architecture, the internal schema was the view of data that involved data management technology. This was as opposed to the external schema that reflected the view of each person in the organization, or the conceptual schema
Conceptual schema
A conceptual schema or conceptual data model is a map of concepts and their relationships. This describes the semantics of an organization and represents a series of assertions about its nature...
that was the integration of a set of external schemas. Subsequently the internal schema was recognized to have two parts:
The logical schema
Logical schema
A Logical Schema is a data model of a specific problem domain expressed in terms of a particular data management technology. Without being specific to a particular database management product, it is in terms of either relational tables and columns, object-oriented classes, or XML tags...
was the way data were represented to conform to the constraints of a particular approach to database management. At that time the choices were hierarchical and network. Describing the logical schema, however, still did not describe how physically data would be stored on disk drives. That is the domain of the physical schema. Now logical schemas describe data in terms of relational tables and columns, object-oriented classes, and XML
XML
Extensible Markup Language is a set of rules for encoding documents in machine-readable form. It is defined in the XML 1.0 Specification produced by the W3C, and several other related specifications, all gratis open standards....
tags. A single set of tables, for example can be implemented in dozens of different ways, up to and including the architecture where some rows are on a computer in Lagos
Lagos
Lagos is a port and the most populous conurbation in Nigeria. With a population of 7,937,932, it is currently the third most populous city in Africa after Cairo and Kinshasa, and currently estimated to be the second fastest growing city in Africa...
and others are on a computer in Warsaw
Warsaw
Warsaw is the capital and largest city of Poland. It is located on the Vistula River, roughly from the Baltic Sea and from the Carpathian Mountains. Its population in 2010 was estimated at 1,716,855 residents with a greater metropolitan area of 2,631,902 residents, making Warsaw the 10th most...
.
This is the physical schema.