Editing Physical schema (section)

==Physical schema==
{{Unreferenced section|date=February 2017}}
''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 Database|Oracle RDBMS]], Sybase SQL Server, etc.).

In the [[ANSI-SPARC Architecture|ANSI/SPARC Architecture]] [[three schema approach]], the ''internal schema'' is the view of data that involved data management technology. This is as opposed to an ''external schema'' that reflects an individual's view of the data, or the ''[[conceptual schema]]'' that is the integration of a set of external schemas.

Subsequently{{Citation needed|date=June 2012}} 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 database model|hierarchical]] and [[Network model (database)|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.