Autonomous Transaction Processing supports private access from Oracle Cloud Infrastructure resources in a VCN through a service gateway.
A service gateway allows connectivity to Autonomous Transaction Processing from private IP addresses in private subnets without requiring an Internet Gateway in your VCN. After a service gateway is configured, there are no special steps required to connect to Autonomous Transaction Processing. Use the same connection steps as described in this chapter, depending on your application type or the client tool you are using to connect to the database.
See Access to Oracle Services: Service Gateway for details.