System Catalogue : A repository of information describing the data in the database, that is the meta-data or data about data.
Data Dictionary (also called system catalogue) stores meta-data that is, data about data, such as :
Information about relations
- Names of relations.
- Names and Types of attributes of each relation.
- Names and Definitions of views.
- Integrity constraints.
User and accounting information, including passwords.
- Names of authorized users.
- Accounting information about users.
- Passwords or other information used to authenticate Statistical and Descriptive data.
- Number of tuples in each relation.
- Method of storage for each relation.