Data Dictionary

 

  • Nature of a Data Dictionary (DD)
  • Rationale for a DD
  • Structure of a DD
  • Typical DD Contents
  • Using SQL to View DD in Oracle
  • grant and revoke Statements

 

Nature of a DD

  • A database contains information about entities of interest to users in an organization
  • When created, the database itself becomes an “entity” about which information must be kept for various data administration purposes
  • Data dictionary (or system catalog) is a database about the database
  • Contents of a DD are commonly referred to as metadata
  • DD can be updated, queried much as a “regular” database
  • DBMS often maintains the DD

 

    Rationale for a DD

  • Provides a summary of the structure of the database

–       helps DBA manage the database

–       informs users of database scope

  • Facilitates communication between users and database administrators
  • Allows the DBMS to manage the creation, access, and modification of tables and their components

 

Structure of a DD

  • DD can be integrated with the DBMS or stand-alone
  • Relational systems all have some form of integrated DD (e.g., Oracle)
  • Integrated DD is usually active, meaning it is automatically updated to reflect changes in the database
  • A stand-alone DD is not directly linked to the database and must be updated manually

 

Typical DD Contents

  • Data elements

–       names, data type

  • Tables

–       owner, creation date, access specifications, size

  • Indexes

–       name, attributes involved, creation date

  • Authorized users

–       names, type(s) of access

  • Integrity Constraints

 

 

 

 

 

 

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