Always wanted to see all Oracle parameters? Including the hidden ones?

The command “show parameter” will show you the non-hidden ones and the already set hidden ones, but will not show you the hidden parameters
that were not set explicitly and their default values.

The following query will show you all the parameters including their current and default values:

select par.ksppinm name,
       val.ksppstvl value,
       val.ksppstdf default_value
from   x$ksppi  par,
       x$ksppcv val
where  par.indx=val.indx;