How to Login to Oracle Cloud Database on port 1521 using SSH tunnel with Linux client
$ ssh -i private-key-file -L local-port:target-ip-address:target-port opc@target-ip-address
private-key-file is the path to the SSH private key file.
local-port is the number of an available port on your Linux system. Specify a port number greater than 1023 and less than 49152 to avoid conflicts with ports that are reserved for the system. As a good practice, and for the sake of simplicity, you should specify the same port number as the one to which you are creating a tunnel.
target-ip-address is the IP address of the target compute node in xyz.xyz.xyz.xyz format.
target-port is the port number to which you want to create a tunnel.
If this is the first time you are connecting to the target compute node, the ssh utility prompts you to confirm the public key. In response to the prompt, enter yes.
After the SSH tunnel is created, you can access the port on the target compute node by specifying localhost:local-port on your Linux system