Recovering undo tablespace from corrupted undo Datafile

  alter system set undo_management=manual scope=spfile;
  shu immediate;
  startup mount;
  alter database datafile 'C:\APP\ADMINISTRATOR\ORADATA\TSTCLONE\UNDOTBS01.DBF' offline drop;
  alter databae open;
  drop tablespace undotbs1;
  create undo tablespace undotbs2 datafile 'C:\app\Administrator\oradata\ANKARA\UNDOTBS01.DBF'  size 100M   REUSE AUTOEXTEND ON NEXT  5120K MAXSIZE  2000M;
  alter system set undo_management=auto scope=spfile;
  alter system set undo_retention = 900 scope = both;
  shu immediate;
  startup;