This image is an architecture diagram of the deployment of an Oracle E-Business Suite application across multiple regions while ensuring high availability.

The architecture consists of a virtual cloud network (VCN) with the bastion, load balancer, application, and database hosts placed in separate subnets of the VCN across two regions. The instances in an availability domain in the second region, called the disaster recovery region, are on standby. The application and database instances are deployed in symmetric topology across regions. In the symmetric topology, you deploy the same number of application and database instances on both the active and standby regions. Two application instances are deployed in each region. Both application instances in the main region are active and the instances in DR region are on standby.

The bastion host is deployed in a public subnet, and all the other instances are deployed in private subnets. The bastion host receives requests through the dynamic routing gateway (DRG) and internet gateway. The DRG is the gateway that connects your on-premises network to your cloud network. To enable communication between the DRG and the customer-premises equipment, use IPSec VPN or Oracle Cloud Infrastructure FastConnect. To access your bastion host from the internet, set up an internet gateway (IGW). An IGW is a software-defined router that provides a path for network traffic from your VCN to the internet.

The load balancer instances receive requests over port 8080 or 8888 and send it to the application servers. The application servers process these requests and forward it to the database instances over port 1521. You can access the instances in private subnets over port 22 through the bastion host or the DRG if you have set up an IPSec VPN tunnel between your data center and Oracle Cloud Infrastructure DRG.

To synchronize application servers across regions, use Rsync. To replicate the database across regions, use Oracle Active Data Guard in synchronous mode.