DOCSP-13116 oplog space reclamation might require restart

Author: jmd-mongo

source/tutorial/change-oplog-size.txt

@@ -119,7 +119,13 @@ The following operation runs the ``compact`` command against the
 .. code-block:: javascript
 
    use local
-   db.runCommand({ "compact" : "oplog.rs" } )
+   db.runCommand({ "compact" : "oplog.rs" })
+
+If the disk space allocated to the original oplog size is not 
+reclaimed, restart :binary:`~bin.mongod` and run the above commands 
+again. Restarting :binary:`~bin.mongod` runs recalculations in 
+:doc:`WiredTiger </core/wiredtiger>` that might allow ``compact`` to 
+release more space to the OS.
 
 For clusters enforcing :ref:`authentication <authentication>`, 
 authenticate as a user with the :authaction:`compact` privilege