Init.ora

Show non-default parameters

set pages 100
set lines 100
select name ||'='||decode(type, 2, '''')||value||decode(type, 2, '''') parameter
from   v$parameter
where  1=1
and    isdefault = 'FALSE'
and    value     is not null
order  by name;

Reset/Unset a spfile parameter

alter system reset <parameter> scope=spfile sid='*'