Doubt in considering temp tablespace's free space

Question

Hi All,
Database: oracle 11.2
Operating System: AIX
I want to know how much free space available in my temp tablespace
I ran below scripts
select sum((bytes_free)/1024/1024/1024) GB from v$temp_space_header
+52.904296875+
select (tablespace_size)/1024/1024/1024 tablespace_size_in_gb,
+(allocated_space)/1024/1024/1024 allocated_space_in_gb,+
+(free_space)/1024/1024/1024 free_space_in_gb+
from dba_temp_free_space
tablespace_size_in_gb: 98.9990234375
allocated_space_in_gb: 46.0947265625
free_space_in_gb:151.81640625
So my doubt is which one from above two script gives actual free space information ?
Also in dba_temp_free_space view why free space size > tablespace size ?

Answer 1

v$temp_space_header shows you how big the temp tablespace has got since the database was restarted. It doesn't give you the current free/used space.
See the link for dba_temp_free_space, but I think it may be the way it reports free space which is why you're seeing it as more than the actual tablespace. As you can see form the description "space that is currently allocated and available for resuse" is calculated for both allocated space and free space.
http://docs.oracle.com/cd/B28359_01/server.111/b28320/statviews_5056.htm
>
ALLOCATED_SPACE = space that is currently allocated and used + space that is currently allocated and available for reuse
FREE_SPACE = space that is currently allocated and available for reuse + space that is currently unallocated>
I use the below script which I've plagiarised from somewhere ages ago to get the used/free temp space.
SELECT   A.tablespace_name tablespace, D.mb_total,
         SUM (A.used_blocks * D.block_size) / 1024 / 1024 mb_used,
         D.mb_total - SUM (A.used_blocks * D.block_size) / 1024 / 1024 mb_free
FROM     v$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;