The procedure to enable port 1521 on the ODCS is as follows:

1. As shown earlier, navigate to DB Systems and click the database to be connected.
2. Click on Virtual Cloud Network.
3. Under Security Lists, navigate to the corresponding subnet.

4. Click Default Security List For <Target Database>. The security list page will be displayed.
5. Click on Edit All Rules.
6. Add an ingress rule to allow any incoming traffic from the public internet to reach port 1521 on this database node with the following settings:
   •  SOURCE CIDR: 0.0.0/0
   • IP PROTOCOL: TCP
   • SOURCE PORT RANGE: All
   • DESTINATION PORT RANGE: 1521
   • Allows: TCP traffic for ports: 1521