The below query used to check the current database size

set lines 300
select round(sum(used.bytes)/1024/1024/1024) || ' GB' "Database Size", round(sum(used.bytes)/1024/1024/1024) - round(free.p/1024/1024/1024) || ' GB' "Used space", 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;