From a networking point of view, Database Migration Service and Cloud SQL are service producers that reside in their own dedicated networks (known as service networks), outside the Virtual Private Cloud (VPC) networks that you use in your Google Cloud project. The goal of configuring network connectivity for a migration process is to ensure that Database Migration Service can reach your source Oracle database and the destination Cloud SQL for PostgreSQL instance.
Before you configure the source or destination database instances, we recommend that you consider what networking methods you can use to establish the necessary network connections. See the following pages:
Networking overview describes the high-level, end-to-end migration networking landscape.
Source networking methods focuses on the source database connectivity.
Destination networking methods focuses on the destination database connectivity.
For a complete, step-by-step migration walkthrough, see Oracle to Cloud SQL for PostgreSQL migration guide.