diff --git a/docs/admin_api/purge_history_api.rst b/docs/admin_api/purge_history_api.rst
index 2da833c82762d0490d63a8e9d1ab814b35761a5f..a5c3dc81499a30285be10e4fbf44e91b99fcafc3 100644
--- a/docs/admin_api/purge_history_api.rst
+++ b/docs/admin_api/purge_history_api.rst
@@ -61,3 +61,11 @@ the following:
     }
 
 The status will be one of ``active``, ``complete``, or ``failed``.
+
+Reclaim disk space (Postgres)
+-----------------------------
+
+To reclaim the disk space and return it to the operating system, you need to run
+`VACUUM FULL;` on the database.
+
+https://www.postgresql.org/docs/current/sql-vacuum.html