Backup types in SQL Server: Judge the statement: "A differential backup makes a copy of the entire database."

Introduction / Context: SQL Server supports several backup types: full, differential, and transaction log. Knowing what each captures is essential for designing backup and restore strategies that balance speed, storage, and recovery point objectives.

Given Data / Assumptions:

• A prior full backup exists (required baseline for differentials).
• Differentials are cumulative since the last full backup.
• Standard SQL Server backup semantics apply.

Concept / Approach: A full backup copies the entire database at the time of the backup. A differential backup copies only the extents changed since the most recent full backup (tracked via the differential changed map). A transaction log backup copies the log records to support point-in-time recovery in FULL or BULK_LOGGED recovery models. Therefore, a differential is not a full copy of the database; it is a smaller, incremental capture of changes since the last full.

Step-by-Step Solution:

Verification / Alternative check: Inspect msdb backup history and differential sizes; observe faster differentials when few changes occurred.

Why Other Options Are Wrong:

• Correct (option b) misstates differential behavior.
• Small DB / DBCC: Size or DBCC checks do not change backup semantics.
• Recovery model: It affects log backups, not differential meaning.

Common Pitfalls: Confusing differential with incremental log backups; forgetting that differentials grow larger over time until the next full backup.

Final Answer: Incorrect