What is the effect described for VACUUM in Delta Lake?

• A. Removes unreferenced files.
• B. Removes unreferenced and old files based on retention threshold.
• C. Keeps all archived files for auditing.
• D. Deletes all data older than 30 days.

Answer: (B)

Vacuum in Delta Lake reclaims storage by removing data files that are no longer part of the table’s active history. Delta keeps a transaction log that tracks which files are referenced by each version. When files become unreferenced (for example, after updates or deletes create newer versions), Vacuum deletes those files, but only after they’ve aged past the retention threshold you specify. This combination—removing unreferenced files and applying a retention period—ensures you don’t lose data still reachable by older snapshots, while freeing up space.

So the effect is to remove both unreferenced files and those older than the configured retention window. It’s not about archiving for auditing, and it’s not a blanket deletion of all data older than a fixed date.