set serveroutput on
declare   
   free_blocks number;   
  begin   
     DBMS_SPACE.FREE_BLOCKS('SCOTT'
                          , 'EMP'
                          ,'TABLE'
                          ,0
                          ,free_blocks);  
     dbms_output.put_line('Freie Blöcke = '||free_blocks);   
end;
/