Data Dictionary / Metadata

Data Dictionary / Metadata:

A metadata (also called the data dictionary) is the data about the data. It is the self-describing nature of the database that provides program-data independence. It is also called as the System Catalog. It contains all the information about the data objects.  It is like storing all up-to-date information about the objects like tables, columns, index, constraints, functions etc.

Data Dictionary consists of the following information:

·        Name of the tables in the database

·        Constraints of a table i.e. keys, relationships, etc.

·        Columns of the tables that related to each other

·        Owner of the table

·        Last accessed information of the object

·        Last updated information of the object

Data dictionary is used to actually control the database operation, data integrity and accuracy. Metadata is used by developers to develop the programs, queries, controls and procedures to manage and manipulate the data. Metadata is available to database administrators (DBAs), designers and authorized user as on-line system documentation. This improves the control of database administrators (DBAs) over the information system and the user's understanding and use of the system.

Data dictionary may be either active or passive. An active data dictionary (also called integrated data dictionary) is managed automatically by the database management software. It is consistent with the current structure and definition of the database. Most of the relational database management systems contain active data dictionaries that can be derived from their system catalog.

The passive data dictionary (also called non-integrated data dictionary) is the one used only for documentation purposes. Data about fields, files, people and so on, in the data processing environment are.

Functions of the data dictionary:

•   It defines the data objects of each user in the database. As we know, we cannot remember all the tables, views, constraints, etc., so the user can easily search them when any Data Definition Language (DDL) fired, then the database searches for the data dictionary. The DBMS software updates the object.

•   It gives us the report about the data and the resources which the objects are using.

•  It allows seeing the tables and views to those users who have the proper rights to access the database. Thus, it controls the access of the database.

Advantages of the data dictionary

•   The data dictionary used so that we can remove the duplicity in the data definition.

•   As it provides documentation. So it is a valuable reference for any organization.

•   It helps the analysts in simplifying the structure so that it can meet the requirement of the data of the system.

•     It helps in improving the communication between the user and the system analyst.

•   Maximum of the database management system contains the data dictionary as a standard feature.

•   Through this, new database administrators can easily understand the database of the system.

•   The database administrator can easily track any problem in the database.

-profshardulp.patil@gmail.com