In database administration, what is a “data dictionary”? Select the best description of what a data dictionary file typically contains for all tables/files in a database system.

Introduction / Context:
A data dictionary (also called a system catalog or metadata repository) is the authoritative reference for the structure and properties of the data stored in a database. It tells designers, developers, and administrators how data is organized, which constraints apply, and how applications should interact with tables and columns. Understanding what a data dictionary contains helps you distinguish metadata from user data.

Given Data / Assumptions:

• The question asks what a data dictionary file typically contains.
• Options list field names, data types, and widths—classic column-level metadata.
• We assume a conventional relational DBMS or similar cataloged system.

Concept / Approach:
A data dictionary stores metadata, not the actual business records. Core entries include: table names; column (field) names; data types (e.g., integer, date, varchar); lengths/widths and precision/scale; default values; nullability; key definitions; indexes; views; constraints; and sometimes user privileges, synonyms, and dependencies. Because the metadata is used by the DBMS engine and tooling, it must be consistent and complete.

Step-by-Step Solution:
Identify what each option represents: names, types, and widths are all standard column metadata.Confirm that a proper dictionary records all three to support validation, storage, and query planning.Therefore, select the inclusive choice that covers all listed metadata elements.

Verification / Alternative check:
Most DBMS expose data dictionary views (for example, INFORMATION_SCHEMA in SQL-standard systems) that enumerate columns, data types, maximum lengths, constraints, and indexes. This confirms that names, types, and widths are cataloged.

Why Other Options Are Wrong:

• Only names or only types or only widths: A real dictionary includes all of these and more.
• None of the above: Incorrect because these items are indeed dictionary contents.

Common Pitfalls:
Confusing a data dictionary (metadata) with a data repository (actual records). Another pitfall is assuming widths are irrelevant; they are essential for storage allocation and validation of input lengths.

Final Answer:
All of the above