Informações das tablespaces - Oracle

select substr(a.tablespace_name,1,20) "Tablespaces",
(b.BYTES/1048576) as "TotalMB",
(b.BYTES/1048576)-(c.BYTES/1048576) as "UsedMB",
(c.BYTES/1048576) as "FreeMB"
from dba_tablespaces a,
(select tablespace_name,sum(bytes) as "BYTES" 
from dba_data_files 
group by tablespace_name ) b,
(select tablespace_name,sum(bytes) as "BYTES" 
from dba_free_space  
group by tablespace_name) c
where
a.tablespace_name = b.tablespace_name(+)
and b.tablespace_name = c.tablespace_name(+)
order by a.tablespace_name;