Data Dictionary is one of the very important components of a database that stores data definitions and characteristics. As we already know that data about data is called Metadata. Similarly, the Data dictionary in DBMS provides self-describing characteristics.
Types of Data Dictionary in DBMS
Data Dictionary is of two types – standalone and integrated.
An integrated data dictionary is included with the DBMS. In older database management systems, a DBA has to include an external data dictionary but these days, DBMS contains an inbuild data dictionary which is frequently updated by the RDBMS.
Also read: Difference between DBMS and RDBMS
Also, the data dictionaries can be classified into active and passive. The data dictionary that is automatically updated by the DBMS with every database access is called an active data dictionary and the data dictionary that uses a batch process to run and is not updated automatically is called a passive data dictionary. During a query access process, the information from the data dictionary is accessed.
Moreover, the main function of the data dictionary is to store descriptions of all the objects used during the usage of the database. Integrated data dictionaries often only include metadata for the data that is under DBMS management.
The DBA can describe and manage all of the organization’s data using stand-alone data dictionaries, regardless of whether they are computerized. Regardless of the data dictionary’s format, its presence of it greatly enhances communication between database designers and end users. The DBA can also resolve data conflicts with the aid of the data dictionary.
Although, there is no standard format for the information stored in the data dictionary several features are common. For example, the data dictionary typically stores descriptions of all:
- Data elements are defined in every database’s table. The name, datatypes, display formats, internal storage formats, and validation procedures are specifically kept in the data dictionary. The data dictionary describes how, where, and by whom an element is used.
- Tables define in all databases. The data dictionary may record information such as the name of the table’s creator, the date of creation, access permissions, the number of columns, and so forth.
- Indexes define for each database table. The DBMS records certain index properties, the creation date, the location, the attributes utilized, and at least the index name for each index.
- Definition of databases: who created each database, the date of creation where the database is located, who the DBA is, and so on.
- End users and The Administrators of the database.
- Programs that access databases, such as screen formats, report formats, application formats, SQL queries, and others.
- Access authorization for all users of all databases.
- The connections and cardinality of the relationships among the data pieces, as well as whether they are required or optional.
So, in this article, we learned about the data dictionary which is one of the very common terms that is used in a Database Management System.
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