The image shows an architecture diagram of the process to migrate a database from on-premises to the cloud using zero downtime migration (ZDM).
The Oracle Cloud Region has one availability domain with a Regional Public Subnet that contains a Bastion Host, and a Regional Private Subnet that contains an Oracle DB System instance. The region has a VCN, Dynamic Routing Gateway, Internet Gateway, Service Gateway, and Object Storage for RMAN backups.
The on-premises data center has a Bastion Host. SQL*Net verification is performed between the on-premises database and the DB System in the cloud. SQL*Net travels through the Internet Gateway to the Bastion Host in the cloud to the DB System.
Also on-premises is an Oracle Database Enterprise Edition (16 cores), storage, and a ZDM Service Host. The ZDM Service Host uses ssh to connect to the on-premises database and ssh through the Internet Gateway to the Bastion Host in the cloud and then to the DB System.
Using https, Oracle RMAN Backups are sent from the ZDM Service Host to Object Storage in Oracle Cloud Region. Oracle RMAN Restore goes from Object Storage through the Service Gateway to the DB System in Availability Domain 1.