How to see hidden parameters in Oracle

To see hidden parameters in Oracle :

set echo off lines 149 pages 9999 feed off
clear col
clear break
clear compute
ttitle off
btitle off

COLUMN Param FORMAT a42 wrap head 'Underscore Parameter'
COLUMN Descr FORMAT a75 wrap head 'Description'
COLUMN SessionVal FORMAT a7 head 'Value|Session'
COLUMN InstanceVal FORMAT a7 head 'Value|Instnc'
ttitle skip 1 center 'All Underscore Parameters' skip 2

SELECT
a.ksppinm Param ,
b.ksppstvl SessionVal ,
c.ksppstvl InstanceVal,
a.ksppdesc Descr
FROM
x$ksppi a ,
x$ksppcv b ,
x$ksppsv c
WHERE
a.indx = b.indx AND
a.indx = c.indx AND
a.ksppinm LIKE '/_%' escape '/'
ORDER BY 1;