--Display the free space, and the space used,
--for each tablespace.
COLUMN tablespace_name HEADING 'Tablespace' FORMAT A20
COLUMN free_bytes HEADING 'Free Bytes' FORMAT 999,999,999
COLUMN used_bytes HEADING 'Used Bytes' FORMAT 999,999,999
COLUMN total_bytes HEADING 'Total Bytes' FORMAT 999,999,999

--Print grand totals
BREAK on REPORT
COMPUTE SUM LABEL 'Totals' OF free_bytes ON REPORT
COMPUTE SUM LABEL 'Totals' OF used_bytes ON REPORT
COMPUTE SUM LABEL 'Totals' OF total_bytes ON REPORT

SELECT free_space.tablespace_name, free_bytes, used_bytes,
       free_bytes + used_bytes total_bytes
  FROM
  (
    SELECT tablespace_name,
	   SUM(bytes) free_bytes
      FROM  dba_free_space
    GROUP BY tablespace_name
  ) free_space,
  ( SELECT tablespace_name,
	   SUM(bytes) used_bytes
      FROM  dba_extents
    GROUP BY tablespace_name
  ) used_space
 WHERE free_space.tablespace_name(+) = used_space.tablespace_name;

COMMIT;