Scripts to find USED,FREE and total DataBase sizes

--> Script to find Total DB size:

select a.data_size+b.temp_size+c.redo_size "total_size"
from ( select sum(bytes)/1024/1024/1024 data_size
         from dba_data_files ) a,
     ( select nvl(sum(bytes)/1024/1024/1024,0) temp_size
         from dba_temp_files ) b,
     ( select sum(bytes)/1024/1024/1024 redo_size
         from sys.v_$log ) c;


--> Script to find Total and Free DB sizes:

col "Database Size" format a20
col "Free space" format a20
select round(sum(used.bytes) / 1024 / 1024 /1024) || ' GB' "Database Size"
,      round(free.p / 1024 / 1024 /1024) || ' GB' "Free space"
from (select bytes from v$datafile
      union all
      select bytes from v$tempfile
      union all
      select bytes from v$log) used
,    (select sum(bytes) as p from dba_free_space) free
group by free.p
/

--> Script to find USED DB size:

SELECT round(SUM(bytes)/1024/1024/1024) "GB" FROM dba_segments;

--> Script to report true free space within the used portion of the TEMPFILE:

SELECT   A.tablespace_name tablespace, D.mb_total,
         SUM (A.used_blocks * D.block_size) / 1024 / 1024 mb_used,
         D.mb_total - SUM (A.used_blocks * D.block_size) / 1024 / 1024 mb_free
FROM     v$sort_segment A,
         (
         SELECT   B.name, C.block_size, SUM (C.bytes) / 1024 / 1024 mb_total
         FROM     v$tablespace B, v$tempfile C
         WHERE    B.ts#= C.ts#
         GROUP BY B.name, C.block_size
         ) D
WHERE    A.tablespace_name = D.name
GROUP by A.tablespace_name, D.mb_total;