SQL & PL/SQL :: Bulk Insert Dummy Data Into Table

I have a table emp as mentioned below:

SELECT * FROM EMP_TEST;

EMP_TEST
-----------------------------------------------------
ENO EFIRSTNAME ESECONDNAME DEPTNO
1 JOHN PAI 10
2 ABC DEF 20
3 EFG GHI 30

Now the primary key in this above table is pk_emp_test_eno on eno.

I have a requirement where i need to dump some dummy data (600000000 numbers of data ) into the emp_test based on these existing data without disabling the constraints (maintaining unique constraint for each record). And while inserting i want to commit after every 1000 insertion.

in bulk inserting dummy datas into the table as it is taking much more time to insert into the same.