INSERT ALL
INTO o_item (o_item_id, PROD_ID, PRICE, L_Total, Q_ORDER, Q_SHIP, L_NUM)
  VALUES ('LD_'||o_item_seq.NEXTVAL, PRODUCT_ID, PRICE, L_Total, Q_ORDER, Q_SHIP, L_NUM)
INTO o_item_REL (O_ID, o_item_id)
  VALUES (o_id, 'LD_'||o_item_seq.CURRVAL)
SELECT A.PROD_ID, D.O_id, A.PRICE, A.L_Total, A.Q_ORDER, Z.Q_SHIP, A.L_NUM
FROM o_load A, O_item C, o_item_REL B, ord D
WHERE A.prod_id = C.prod_id
AND A.j_ref_num = C.n_ord_id
AND A.n_ord_id = D.n_ord_id
AND C.o_item_id = B.o_item_id
AND (A.N_ORD_ID not in (select F.n_ord_id from o_item F where F.n_ord_id = a.n_ord_id)
    OR (A.N_ORD_ID in (select F.n_ord_id from o_item F where F.n_ord_id = a.n_ord_id)
       AND A.prod_id not in (select F.prod_id from o_item F where F.n_ord_id = a.n_ord_id)
       )
    )
/
commit;

SQL> drop sequence s1;

Sequence dropped.

SQL> drop sequence s2;

Sequence dropped.

SQL> create table p (id1 integer, id2 integer);

Table created.

SQL> create table c (id1 integer, id2 integer);

Table created.

SQL> create sequence s1;

Sequence created.

SQL> create sequence s2;

Sequence created.

SQL> insert all 
  2  into c values (s1.currval, s2.nextval)
  3  into p values (s1.nextval, s2.nextval)
  4  select 1 from dual connect by level <= 3
  5  /

6 rows created.

SQL> select * from p;
       ID1        ID2
---------- ----------
         1          1
         2          2
         3          3

3 rows selected.

SQL> select * from c;
       ID1        ID2
---------- ----------
         1          1
         2          2
         3          3

3 rows selected.

SQL> create table p (pid integer primary key, val integer);

Table created.

SQL> create table c (
  2    cid integer primary key, 
  3    pid integer,
  4    constraint c_p_fk foreign key(pid) references p 
  5      deferrable initially immediate);

Table created.

SQL> create sequence s1;

Sequence created.

SQL> create sequence s2;

Sequence created.

SQL> set constraint c_p_fk deferred;

Constraint set.

SQL> insert all 
  2  into p values (s1.nextval, 0)
  3  into c values (s2.nextval, s1.currval)
  4  select 1 from dual connect by level <= 3
  5  /

6 rows created.

SQL> set constraints all immediate;

Constraint set.
...

ORA-02291: integrity constraint (%s.%s) violated - parent key not found
 *Cause: A foreign key value has no matching primary key value.
 *Action: Delete the foreign key or add a matching primary key.