Oracle Database fires multiple triggers in an unspecified, random order, if more than one trigger of the same type exists for a given statement; that is, triggers of the same type for the same statement are not guaranteed to fire in any specific order.
Execution steps of trigger.
http://docs.oracle.com/cd/B28359_01/server.111/b28318/triggers.htm#CNCPT418
DBA_TRIGGER_ORDERING description
http://docs.oracle.com/cd/B28359_01/server.111/b28320/statviews_2107.htm#REFRN20581
sample:
create or replace trigger trigger_01
before insert on test
for each row
follows trigger_02
....
create or replace trigger trigger_02
before insert on test
for each row
