Unveil Undocumented Initialization Parameters

Configuring the Oracle database using the initialization parameters is a vital part of database tuning. There are a lot of parameters whose description can be found in the documentation. Here is how to unveil the undocumented ones. Their names always start with an underscore:

select p.ksppinm "Parameter"
,      p.ksppdesc "Description"
,      c.ksppstvl "Session Value"
,      s.ksppstvl "Instance Value"
from   x$ksppi p
,      x$ksppcv c
,      x$ksppsv s
where  p.inst_id = userenv('instance')
and    p.indx = c.indx
and    p.indx = s.indx
and    p.ksppinm LIKE '#_%' escape '#'
order by p.ksppinm
/

These parameters should only be used with care and under instruction of Oracle Support or an experienced DBA.

One useful parameter is _trace_files_public. Trace files can be made publicly accessible in development and test environments.