Which statement about the VACUUM operation is accurate?

• A. It moves data
• B. It duplicates data
• C. It compresses files
• D. It deletes unreferenced files older than the retention policy

Answer: (D)

The idea being tested is that VACUUM is a cleanup operation in modern data lake systems that reclaims storage by removing data files no longer referenced by any current version of the dataset. It works in conjunction with a retention policy: only files that are unreferenced and older than the defined retention window are deleted. This safeguards ongoing reads or time-travel queries that might still need older data, while freeing up space by removing obsolete files. VACUUM does not move data, duplicate data, or compress files—that’s handled by other processes. So the statement that VACUUM deletes unreferenced files older than the retention policy best captures its purpose.