in Transit routing through a private IP in the VCN you set up an instance in the VCN to act as a firewall or intrusion detection system to filter or inspect the traffic between the on-premises network and Oracle Services Network.
The Networking service lets you implement network security functions such as intrusion detection, application-level firewalls In fact, the IDS model can be host-based IDS (HIDS) or network-based IDS (NIDS). HIDS is installed at a host to periodically monitor specific system logs for patterns of intrusions. In contrast, an NIDS sniffs the traffic to analyze suspicious behaviors. A signature-based NIDS (SNIDS) examines the traffic for patterns of known intrusions. SNIDS can quickly and reliably diagnose the attacking techniques and security holes without generating an over-whelming number of false alarms because SNIDS relies on known signatures.
However, anomaly-based NIDS (ANIDS) detects unusual behaviors based on statistical methods. ANIDS could detect symptoms of attacks without specific knowledge of details. However, if the training data of the normal traffic are inadequate, ANIDS may generate a large number of false alarms.

https://docs.cloud.oracle.com/en-us/iaas/Content/Resources/Assets/whitepapers/best-practices-for-dr-on-oci.pdf All three Data Guard configurations are fully supported on Oracle Cloud Infrastructure. However, because of a high risk of production outage, we don't recommend using the maximum protection mode for your Data Guard configuration.
We recommend using the maximum availability mode in SYNC mode between two availability domains (same region), and using the maximum availability mode in ASYNC mode between two regions. This architecture provides you the best RTO and RPO without causing any data loss. We recommend building this architecture in daisy-chain mode: the primary database ships redo logs to the first standby database in another availability domain in SYNC mode, and then the first standby database ships the redo logs to another region in ASYNC mode. This method ensures that your primary database is not doing the double work of shipping redo logs, which can cause performance impact on a production workload.

This configuration offers the following benefits:
No data loss within a region.
No overhead on the production database to maintain standbys in another region.
Option to configure lagging on the DR site if needed for business reasons.
Option to configure multiple standbys in different regions without any additional overhead on the production database. A typical use case is a CDN application Bottom of Form