Recovery without UNDO Tablespace DataFiles

If you encounter a situation where an UNDO datafile is missing from a cloned database you can
actually drop and recreate the UNDOTBS tablespace with

       a) Shutdown immediate
       b) Edit the init.ora to unset "undo_management=AUTO" {Oracle then ignores the setting of     

           "undo_tablespace"}
       c) Startup
       d) Drop Tablespace UNDOTBS
       e) Create UNDO Tablespace UNDOTBS datafile ...
        f) Shutdown
       g) Reset "undo_management=AUTO"
       h) Startup Database.