Get level of events, can be used to check which events are set.
alter session set events '10046 trace name context forever, level 12';
alter session set events '10051 trace name context forever, level 1';
alter session set events '10053 trace name context forever';
--
-- Note, neither 10046 nor 10053 is reported...
--
declare
lvl number;
begin
for ev in 10000 .. 10999 loop
sys.dbms_system.read_ev (ev, lvl);
if lvl > 0 then
dbms_output.put_line ('Event ' || ev || ' is set to level ' || lvl);
end if;
end loop;
end;
/