Correct tablespace script.

select a.tablespace_name,round(a.tablespace_size,2) Tot_GB,round(b.used,2) Used_GB, round(a.tablespace_size-b.used,2) Free_GB,

round(b.used*100/a.tablespace_size) USEDPCT

from (select dba_data_files.tablespace_name,sum(decode(autoextensible,'YES',MAXBYTES,BYTES))/1024/1024/1024 Tablespace_Size

from dba_data_files group by tablespace_name) a,

(select tablespace_name,sum(bytes)/1024/1024/1024 used from dba_segments group by tablespace_name) b

where a.tablespace_name=b.tablespace_name and round(b.used*100/a.tablespace_size) > 30 order by USEDPCT desc;