X$KQ  Kernel query:

x$kqfta:Display x$ table name .

select kqftanam from x$kqfta;

x$KS Kernel service:

x$ksppi:
Contains a record for all documented and undocumented (starting with an underscore) parameters.

**Display the value of hidden parameter :
select SELECT ksppinm, ksppstvl
  FROM x$ksppi a, x$ksppsv b
 WHERE a.indx = b.indx AND ksppinm = '_sqlmon_max_planlines';