The VACUUM command is used in Delta Lake to clean up and remove data files that are no longer referenced by a Delta table's transaction log and are older than a specified retention period. When data in a Delta table is updated or deleted, the old files are not immediately removed to support features like time travel. The VACUUM command permanently deletes these stale files. By default, the retention period is seven days, which directly aligns with the requirement to remove files older than seven days that are no longer in use. This is a critical maintenance operation for managing storage costs and data lifecycle in a Fabric lakehouse.

B. COMPUTE: The COMPUTE STATISTICS command is used to collect statistics about the data in a table, which helps the query optimizer generate more efficient plans. It does not remove any files.

C. OPTIMIZE: The OPTIMIZE command improves query performance by compacting many small files into fewer, larger files. It reorganizes active data but does not delete old, unreferenced data files.

D. CLONE: The CLONE command creates a copy of an existing Delta table at a specific version. It is used for data replication or creating development/test environments, not for cleaning up the source table.

1. Microsoft Fabric Documentation - Table maintenance: "The VACUUM command is a crucial table maintenance operation that helps manage storage costs and maintain compliance by removing old and unreferenced data files... By default

VACUUM sets a seven-day retention threshold." This source directly supports the use of VACUUM for removing files older than seven days.

Source: Microsoft Learn. (2024). Table maintenance in Microsoft Fabric. Section: "VACUUM".

2. Delta Lake Documentation - VACUUM: "Recursively vacuum directories associated with the Delta table and remove data files that are no longer in the latest state of the transaction log for the table and are older than a retention threshold."

Source: Delta.io Documentation. Vacuum a Delta table (garbage collection).

3. Microsoft Fabric Documentation - OPTIMIZE: "The OPTIMIZE command is a table maintenance operation that aims to enhance query performance and reduce storage costs by compacting small files into larger ones." This confirms OPTIMIZE is for file compaction

not deletion of old versions.

Source: Microsoft Learn. (2024). Table maintenance in Microsoft Fabric. Section: "OPTIMIZE".

4. Microsoft Fabric Documentation - CLONE: "The CLONE command creates a copy of a source table to a destination at a specific version. There are two types of clones: deep and shallow." This shows CLONE is for copying

not cleaning.

Source: Microsoft Learn. (2024). CLONE.