查看UNDO 表空间使用情况

Select Sum(bytes / (1024 * 1024)), a.status
    From dba_undo_extents a
   Group By a.status

Select file_name, file_id, bytes / (1024 * 1024 * 1024) g, autoextensible
   From dba_data_files
  Where tablespace_name Like '%UNDO%'