Physical schema

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Physical schema is a term used in data management to describe how data is to be represented and stored (files, indices, et al.) in secondary storage using a particular database management system (DBMS) (e.g., Oracle RDBMS, Sybase SQL Server, etc.).

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 numerous ways, up to and including an architecture where table rows are maintained on computers in different countries.

See also

• Database schema
• Logical schema

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