Incorrect trapping of free space in tablespace

Question

Hi,
We have a script that monitors tablespaces, and flags if they are getting full. The code is shown below......
select tablespace_name from
(select a.tablespace_name, a.physsp/1024/1024 psm,
nvl(b.freesp,0)/1024/1024 fsm,
nvl(b.mfreecnk,0)/1024/1024 mfs,
nvl((a.physsp + c.extdf - c.extdfact),a.physsp)/1024/1024 maxpos,
100*(a.physsp - nvl(b.freesp,0))/nvl((a.physsp + c.extdf - c.extdfact),a.physsp) maxpospct
from
(select tablespace_name, sum(bytes) physsp
from dba_data_files
group by tablespace_name) a,
(select tablespace_name, sum(bytes) freesp, max(bytes) mfreecnk
from dba_free_space
group by tablespace_name) b,
(select distinct tablespace_name, autoextensible ext,sum(maxbytes) extdf
,sum(bytes) extdfact
from dba_data_files
where autoextensible='YES'
group by tablespace_name,autoextensible) c
where b.tablespace_name (+) = a.tablespace_name
and c.tablespace_name (+) = a.tablespace_name
and a.tablespace_name not like '%UNDO%') outer
where ((outer.maxpos - outer.psm) + outer.mfs) < 500
and maxpospct > 90 ;
One tablespace is showing as either failing this test (of being > 90% full and less than 500MB free), but while it is 92% full, it has over 5gb free.....
SELECT a.name, b.tablespace_name,
substr('Free : '||sum(b.bytes)/1024/1024,1,30) File_Size
FROM dba_free_space b, v$database a
GROUP BY b.tablespace_name, a.name
UNION
SELECT a.name, b.tablespace_name,
substr('Total: '||sum(b.bytes)/1024/1024,1,30)
FROM dba_data_files b, v$database a
GROUP BY b.tablespace_name, a.name
ORDER BY 1,2,3;
NAME TABLESPACE_NAME FILE_SIZE
DB12 DATA Free : 5368.75
DB12 DATA Total: 70000
DB12 SYSAUX Free : 10.375
DB12 SYSAUX Total: 280
DB12 SYSTEM Free : 33.0625
DB12 SYSTEM Total: 500
DB12 UNDOTBS1 Free : 3055.75
DB12 UNDOTBS1 Total: 3185
DB12 USERS Free : 4.6875
DB12 USERS Total: 5
10 rows selected.
It is tablespace DATA that is complaining in the first script. This was flagged up first during a session of creating a lot of dropped indexes (data had been reimported), and at first I though it might have been something to do with the recycle bin, but a purge of that made no difference.
What's wrong?
Thanks for your help.

Answer 1

Hi,
We have a script that monitors tablespaces, and flags if they are getting full. The code is shown below......
select tablespace_name from
(select a.tablespace_name, a.physsp/1024/1024 psm,
nvl(b.freesp,0)/1024/1024 fsm,
nvl(b.mfreecnk,0)/1024/1024 mfs,
nvl((a.physsp + c.extdf - c.extdfact),a.physsp)/1024/1024 maxpos,
100*(a.physsp - nvl(b.freesp,0))/nvl((a.physsp + c.extdf - c.extdfact),a.physsp) maxpospct
from
(select tablespace_name, sum(bytes) physsp
from dba_data_files
group by tablespace_name) a,
(select tablespace_name, sum(bytes) freesp, max(bytes) mfreecnk
from dba_free_space
group by tablespace_name) b,
(select distinct tablespace_name, autoextensible ext,sum(maxbytes) extdf
,sum(bytes) extdfact
from dba_data_files
where autoextensible='YES'
group by tablespace_name,autoextensible) c
where b.tablespace_name (+) = a.tablespace_name
and c.tablespace_name (+) = a.tablespace_name
and a.tablespace_name not like '%UNDO%') outer
where ((outer.maxpos - outer.psm) + outer.mfs) < 500
and maxpospct > 90 ;
One tablespace is showing as either failing this test (of being > 90% full and less than 500MB free), but while it is 92% full, it has over 5gb free.....
SELECT a.name, b.tablespace_name,
substr('Free : '||sum(b.bytes)/1024/1024,1,30) File_Size
FROM dba_free_space b, v$database a
GROUP BY b.tablespace_name, a.name
UNION
SELECT a.name, b.tablespace_name,
substr('Total: '||sum(b.bytes)/1024/1024,1,30)
FROM dba_data_files b, v$database a
GROUP BY b.tablespace_name, a.name
ORDER BY 1,2,3;
NAME TABLESPACE_NAME FILE_SIZE
DB12 DATA Free : 5368.75
DB12 DATA Total: 70000
DB12 SYSAUX Free : 10.375
DB12 SYSAUX Total: 280
DB12 SYSTEM Free : 33.0625
DB12 SYSTEM Total: 500
DB12 UNDOTBS1 Free : 3055.75
DB12 UNDOTBS1 Total: 3185
DB12 USERS Free : 4.6875
DB12 USERS Total: 5
10 rows selected.
It is tablespace DATA that is complaining in the first script. This was flagged up first during a session of creating a lot of dropped indexes (data had been reimported), and at first I though it might have been something to do with the recycle bin, but a purge of that made no difference.
What's wrong?
Thanks for your help.