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What is Systen Catalogue in DBMS ?

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.
Physical file organization information.

How relation is stored (sequential/hash/...).
Physical location of relation.
   (a) Operating system file name or
   (b) Disk addresses of blocks containing records of the relation.

Information about indices.
  • Name of the index.
  • Name of relation being indexed.
  • Attributes on which the index is defined.
  • Types of index formed.
Catalog structure can use either specialized data structures designed for efficient access or a set of relations, with existing system features used to ensure efficient access.

A Possible Catalogue Representation : primary keys are underlined
Relation-meta-data = (relation-name, name-of-attributes, storage-organization, location)
Attribute-meta-data = (attribute-name, relation-name, domain-type, position, length)
User-meta-data = (user-name, encrypted-password, group)
Index-meta-data = (index-name, relation-name, index-type, index-attributes)
View-meta-data = (view-name, definition)
What is Systen Catalogue in DBMS ? Reviewed by Hardik Pandya on 7:27:00 PM Rating: 5

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