Simple definition
Active Directory garbage collection periodically removes expired deleted objects from the directory database.
Purpose and use
AD garbage collection performs maintenance including permanent removal of selected deleted objects whose retention has expired.
How does it work?
Cleanup follows directory states and retention periods rather than immediately following every administrator deletion.
Example and verification
When investigating space or deleted objects, inspect state, dates and configuration before considering database intervention.
Points to watch
Logical deletion does not necessarily shrink the database file immediately. Shortening retention without assessing replication can increase lingering-object risk.
In short
Internal maintenance and recoverability should be considered together with replication health.