Is dropping foreign key constriants an event in Oracle? I wrote the following trigger in Oracle:

create or replace trigger foreign_drop before ddl on database
begin
  insert into ddl_log
  select ora_sysevent, ora_dict_obj_owner, ora_dict_obj_name, null, user, 
sysdate
  from dual;
end foreign_drop;


It fires whenever a DDL event happens. But when I drop a foreign key constraint, nothing is recorded. Is dropping a foreign key constraints considered an event? How could I record the action of dropping a foreign key constraint?
The following trigger captures the drop constraint operation.

create or replace trigger foreign_drop after create or alter or drop on database
begin
  dbms_output.put_line('DDL Fired!');
end foreign_drop;
/
SQL&gt; set serveroutput on
SQL&gt; CREATE TABLE t2
( id number,
  CONSTRAINT fk_id
    FOREIGN KEY (id)
    REFERENCES t1(id)
);  2    3    4    5    6  
DDL Fired!

Table created.

SQL&gt; alter table t2 drop constraint fk_id;
DDL Fired!

Table altered.