Hidden parameters sometimes ease the life of DBA but be carefull while using them Oracle usually does not support the usage of hidden parameters without their knowledge and you cant even know the side effects of the parameter.
Here is the query you can use to view the values of hidden parameter. (use it with sys user with sysdba privilages)
/* hidden parameters */
select a.ksppinm name,
b.ksppstvl value,
b.ksppstdf deflt,
decode
(a.ksppity, 1,
‘boolean’, 2,
‘string’, 3,
‘number’, 4,
‘file’, a.ksppity) type,
a.ksppdesc description
from
sys.x$ksppi a,
sys.x$ksppcv b
where
a.indx = b.indx
and
a.ksppinm like ‘\_%’ escape ‘\’
order by
name
Footnote 27/07/2009: I personally start to use Tanel Poder’s script to search both hidden and normal parameters