Problem: PL/SQL + Stored Procedure + Sequence + Trigger + Transaction + Violation Key

Question

I have a violation key when i insert some datas from a stored procedure. Why ???
This is my script :
1) The script of the table :
CREATE TABLE OLLMULTI (
     IDO int NOT NULL ,
     IDL int NOT NULL ,
     T1 varchar2 (2) NOT NULL ,
     IDR int NOT NULL ,
     Constraint pk_outilsllmulti PRIMARY KEY (IDO, IDL, T1) ,
     Constraint u_outilsllmulti unique (IDR) );
2) Now, i want to manage automatic increment field on IDR :
I create a sequence :
create sequence OLLMULTI_sequence increment by 1 start with 1;
I create the trigger :
create or replace trigger OLLMULTI_trigger
before insert on OLLMULTI
for each row when (new.IDR is null)
begin
select OLLMULTI_sequence.nextval into :new.IDR from dual;
end;
3) Now i create my store procedure and, in my procedure i want to insert 6 rows :
Procedure Insert_OLLMULTI( i_IDO in OLLMULTI.IDO%type)
is
pragma AUTONOMOUS_TRANSACTION;
BEGIN
INSERT INTO OLLMULTI (IDO,IDL,T1)
VALUES (i_IDO,2,'GJ');
INSERT INTO OLLMULTI (IDO,IDL,T1)
VALUES (i_IDO,5,'ND');
INSERT INTO OLLMULTI (IDO,IDL,T1)
VALUES (i_IDO,12,'AC');
INSERT INTO OLLMULTI (IDO,IDL,T1)
VALUES (i_IDO,120,'AH');
INSERT INTO OLLMULTI (IDO,IDL,T1)
VALUES (i_IDO,10,'ZG');
INSERT INTO OLLMULTI (IDO,IDL,T1)
VALUES (i_IDO,5,'RB');
commit;
EXCEPTION
WHEN OTHERS THEN
rollback;
raise;
END;
END;
4) The problem :
The violation key on the constrainst u_outilsllmulti appears sometimes on a randome insert. Never the same !
Why ? I think that the sequence is the problem... Or is the problem is the "pragma AUTONOMOUS_TRANSACTION" command ?
Anyone can help me ?

Answer 1

Two ideas:
- Is it possible that there are already records in the table that were
created without using the sequence? A sequence initially starts at 1,
if you already got data you first have to increment it.
- May it be that some inserts happen without your procedure? The trigger
allows to create IDs without using the sequence. Correct, there are already records in my table !!
Thanks. That's right.