What is a data dictionary, and what information does it typically contain?

• A. A data dictionary describes data elements, definitions, data types, allowed values, relationships, and lineage for data assets.
• B. A data dictionary stores actual data values for operational databases.
• C. A data dictionary manages user access control and permissions.
• D. A data dictionary stores query execution plans.

Answer: (A)

A data dictionary is a metadata repository that describes data assets, detailing what each data element means and how it’s used. It typically lists the element name, a precise definition, the data type and size, any allowed values or constraints, whether nulls are permitted, and whether the element acts as a key or participates in relationships with other elements. It also captures data lineage (where the data comes from and how it’s transformed), ownership or stewardship, and when the metadata was created or last updated. This collection of information helps everyone—developers, analysts, and data stewards—understand and use data consistently, enforce standards, and trace data provenance across systems. It doesn’t store actual data values (that’s a database), it doesn’t manage who can access data (that’s security/permissions), and it isn’t about query execution plans (that’s database/optimizer metadata).