/*
changing underscore dynamically

alter system set "_ash_enable"=true;
*/

select *
from   SYS.X$KSPPI
where  substr(KSPPINM,1,1) = '_';

/* or */

column parameter format a40
column session_value format a15
column instance_value format a15
select
        a.ksppinm  parameter,
        b.ksppstvl session_value,
        c.ksppstvl instance_value
  from
        x$ksppi a,
        x$ksppcv b,
        x$ksppsv c
 where
        a.indx = b.indx
    and a.indx = c.indx
    and lower(ksppinm) like lower('%&1%')
    --and substr(ksppinm,1,1)='_'