A physical data model (or
database design) is a representation of a data design as implemented, or intended to be implemented, in a
database management system. In the
lifecycle of a project it typically derives from a
logical data model A logical data model or logical schema is a data model of a specific problem domain expressed independently of a particular database management product or storage technology (physical data model) but in terms of data structures such as relational ta ...
, though it may be
reverse-engineered from a given
database
In computing, a database is an organized collection of data stored and accessed electronically. Small databases can be stored on a file system, while large databases are hosted on computer clusters or cloud storage. The design of databases s ...
implementation. A complete physical data model will include all the
database artifacts required to create
relationships between tables or to achieve performance goals, such as
indexes, constraint definitions, linking tables,
partitioned tables or
clusters. Analysts can usually use a physical data model to calculate storage estimates; it may include specific storage allocation details for a given database system.
seven main databases dominate the commercial marketplace:
Informix,
Oracle,
Postgres,
SQL Server,
Sybase,
IBM Db2 and
MySQL
MySQL () is an open-source relational database management system (RDBMS). Its name is a combination of "My", the name of co-founder Michael Widenius's daughter My, and "SQL", the acronym for Structured Query Language. A relational database ...
. Other RDBMS systems tend either to be legacy databases or used within academia such as universities or further education colleges. Physical data models for each implementation would differ significantly, not least due to underlying
operating-system requirements that may sit underneath them. For example: SQL Server runs only on
Microsoft Windows operating-systems (Starting with SQL Server 2017, SQL Server runs on Linux. It's the same SQL Server database engine, with many similar features and services regardless of your operating system
), while Oracle and MySQL can run on Solaris, Linux and other UNIX-based operating-systems as well as on Windows. This means that the disk requirements, security requirements and many other aspects of a physical data model will be influenced by the RDBMS that a
database administrator
Database administrators (DBAs) use specialized software to store and organize data. The role may include capacity planning, installation, configuration, database design, migration, performance monitoring, security, troubleshooting, as well as ba ...
(or an organization) chooses to use.
Physical schema
''Physical schema'' is a term used in
data management to describe how
data
In the pursuit of knowledge, data (; ) is a collection of discrete Value_(semiotics), values that convey information, describing quantity, qualitative property, quality, fact, statistics, other basic units of meaning, or simply sequences of sy ...
is to be represented and stored (files, indices, ''et al.'') in
secondary storage using a particular
database management system (DBMS) (e.g.,
Oracle RDBMS
Oracle Database (commonly referred to as Oracle DBMS, Oracle Autonomous Database, or simply as Oracle) is a multi-model database management system produced and marketed by Oracle Corporation.
It is a database commonly used for running online ...
, Sybase SQL Server, etc.).
In the
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 the internal schema was recognized to have two parts:
The
logical schema A logical data model or logical schema is a data model of a specific problem domain expressed independently of a particular database management product or storage technology ( physical data model) but in terms of data structures such as relational t ...
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
Extensible Markup Language (XML) is a markup language and file format for storing, transmitting, and reconstructing arbitrary data. It defines a set of rules for encoding documents in a format that is both human-readable and machine-readable ...
''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
*
Conceptual data model
*
Logical data model A logical data model or logical schema is a data model of a specific problem domain expressed independently of a particular database management product or storage technology (physical data model) but in terms of data structures such as relational ta ...
References
External links
FEA Consolidated Reference Model Document(whitehouse.gov) Oct 2007.
{{DEFAULTSORT:Physical Data Model
Data modeling
Data management
ja:スキーマ (データベース)