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What is the data Dictionary or metadata in DBMS?
A Data Dictionary is an integral part of a database. It holds the information about the database and the data that it stores called as metadata.
A meta data is the data about the data.
It is the self-describing nature of databases.
It holds the information about each data element in the database.
Such as names, types, range of values, access authorization, indicate which application program uses the data.
Meta data is used by the developers to develop the program, queries to manage and manipulate the data.
Types of dictionaries
In general, DBMS data dictionaries are of two types. These dictionaries are as follows −
Active data dictionary
It is managed automatically by the data management software.
It is always consistent with the current structure of the database.
Passive data dictionary
It is mainly used for documentation purposes.
It is managed by the user of the system and is modified manually by the user.
The data dictionaries are pictorially represented as follows −
Data in DBMS data dictionary
The data in DBMS data dictionary is explained below −
Schema
Tables
Columns
Constraints
Foreign keys
Indexes
Sequences
Programs
Views
User defined functions
Stored procedures
Triggers
Security
Users
User groups
Privileges
Physical implementation
Partitions
Files
Backups
Storage
Size of tables and indexes in KBs
Number of rows in tables
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