What is MetaData in DBMS?

Metadata, in simple terms, refers to data about data. The term metadata is used for different types of data in different contexts. For example, in images, metadata stores the size, encoding, date of modification, etc. The same is true for videos. In a database, metadata stores all information about the schema itself, the columns, rows, and relations are stored within the metadata of the database.

Define Metadata in DBMS

Metadata in DBMS is characterized as data about data. It describes the context and information about data, the way that data is stored and the various relations among data. Metadata in a relational DBMS stores data about Constraints, Table Relationships, Data Types, Columns, Tables, and so on. Metadata is the value that leads us to the actual data and is an acronym for the detailed data in a database.

Types of Metadata in DBMS

There are four types of metadata in DBMS, namely :

Technical Metadata

Technical Metadata stores information about the way in which data is stored in the Database, i.e. table names, table sizes, data types, values, attributes, primary keys, foreign keys, etc.

Business Metadata

Business metadata contains information about a particular business and the way that the business may handle the data in the database. Information like ownership, Policies of handling data, business rules and regulations, etc are stored as business metadata

Operational Metadata

Operational Metadata stores information about data that is currently under any operation. It represents the data that is used by executive-level managers to perform any task.

Descriptive Metadata

Descriptive Metadata stores descriptive information on any file, folder, image, video, etc. Information like size, encoding, author, date, etc is all descriptive metadata.

Example of Metadata in DBMS

A few examples of metadata in DBMS include:

• For any table in a relational database, its metadata would store the table name, column names, and their types along with information about their primary keys, foreign keys, and so on.
• For any relational schema in a relational database, its metadata would store the relationships between the various tables and their types as well as individual metadata about each table as well
• For a data warehouse, Metadata acts as a dictionary as well as a roadmap to the various modules of that data warehouse

Metadata in Terms of Data Warehouse

Metadata plays a number of roles in a data warehouse

• Metadata acts as a roadmap and a dictionary to the data warehouse
• Metadata acts as a glue that links all parts of a data warehouse
• Building and processing of data warehouse generate metadata and that metadata may then be used by a different method for processing. As such, metadata acts as the central nervous system for a data warehouse
• Metadata defines warehouse objects
• Metadata acts as a directory. This directory helps the decision support system to locate the contents of a data warehouse.

Why is Metadata Necessary in a Data Warehouse?

A data warehouse refers to a large repository of data that can be processed or analyzed for various purposes. Data warehouse stores information of various types and from various sources. As such, not just the data but information like the type of data, its source, the time at which the data was gathered, etc are also valuable information required during the analysis of the data.

All of such information is stored as metadata. Moreover, the Processing of any data also generates a large amount of information which is again stored as metadata and such information can then be used for further processing by other methods.

In this way, metadata is a very important part of a data warehouse.