Fix ORA-30012: undo tablespace 'UNDOTBS1' does not exist or of wrong type

1. shutdown database
2. change parameter use manual management of undo, else you can't open database
undo_management=manual
3. startup database
4. recreate undo tablespace
drop tablespace undotbs1 including contents and datafiles;
create UNDO TABLESPACE "UNDOTBS1" DATAFILE 'F:\ORACLE\ORADATA\ORACLE_SID\UNDOTBS1.ORA' SIZE 200M REUSE AUTOEXTEND ON NEXT 10M MAXSIZE UNLIMITED;
5. restart database
6. check alert log. done.