Table of Contents
Data Dictionary
A data dictionary is a collection of database metadata, which is data about data. One kind of data dictionary is a human view of entities, attributes, and relationships, called a designer's data dictionary. There is usually a data dictionary that is internal to the DBMS, called a system catalog, which contains additional system-generated metadata. A designer's data dictionary can be derived from the system catalog, and the terms “data dictionary” and “system catalog” are often used interchangeably.
Purpose
The purpose of a data dictionary is to make sure that all of the people who design and implement the database are on the same page in light of the entities, attributes, and relationships.
Database Designer's Database
A data dictionary is sometimes called a database designer's database because it defines choices made in light of database design of entities and their characteristics.
- Snippet from Wikipedia: Data dictionary
A data dictionary, or metadata repository, as defined in the IBM Dictionary of Computing, is a "centralized repository of information about data such as meaning, relationships to other data, origin, usage, and format". Oracle defines it as a collection of tables with metadata. The term can have one of several closely related meanings pertaining to databases and database management systems (DBMS):
- A document describing a database or collection of databases
- An integral component of a DBMS that is required to determine its structure
- A piece of middleware that extends or supplants the native data dictionary of a DBMS