oracle tablespace usage

-- Size and usage of tablespaces
SELECT T1.TABLESPACE_NAME,
       T1.BYTES / 1024 / 1024   as                        "bytes_used (Mb)",
       T2.BYTES / 1024 / 1024   as                        "bytes_free (Mb)",
       T2.largest / 1024 / 1024 as                        "largest (Mb)",
       round(((T1.BYTES - T2.BYTES) / T1.BYTES) * 100, 2) percent_used
FROM (
         select TABLESPACE_NAME,
                sum(BYTES) BYTES
         from dba_data_files
         group by TABLESPACE_NAME
     ) T1,
     (
         select TABLESPACE_NAME,
                sum(BYTES) BYTES,
                max(BYTES) largest
         from dba_free_space
         group by TABLESPACE_NAME
     ) T2
where T1.TABLESPACE_NAME = T2.TABLESPACE_NAME
order by ((T1.BYTES - T2.BYTES) / T1.BYTES) desc;