Tablespace Utilization in Oracle

Taken from: http://vsbabu.org/oracle/sect03.html
Usage

TABLESPACE USAGE NOTES:
Tablespace Name - Name of the tablespace
Bytes Used - Size of the file in bytes
Bytes Free - Size of free space in bytes
Largest - Largest free space in bytes



select a.TABLESPACE_NAME,
a.BYTES bytes_used,
b.BYTES bytes_free,
b.largest,
round(((a.BYTES-b.BYTES)/a.BYTES)*100,2) percent_used
from
(
select TABLESPACE_NAME,
sum(BYTES) BYTES
from dba_data_files
group by TABLESPACE_NAME
)
a,
(
select TABLESPACE_NAME,
sum(BYTES) BYTES ,
max(BYTES) largest
from dba_free_space
group by TABLESPACE_NAME
)
b
where a.TABLESPACE_NAME=b.TABLESPACE_NAME
order by ((a.BYTES-b.BYTES)/a.BYTES) desc