Explanation
Archive storage is the most cost effective for archive data

You can set up a single IPSec VPN with a simple layout that you might use for a proof of concept (POC).
Reference: https://docs.cloud.oracle.com/en-us/iaas/Content/Network/Tasks/settingupIPsec.htm

Oracle Cloud Infrastructure's Autonomous Database is a fully managed, preconfigured database environment with two workload types available, Autonomous Transaction Processing and Autonomous Data Warehouse. You do not need to configure or manage any hardware, or install any software. After provisioning, you can scale the number of CPU cores or the storage capacity of the database at any time without impacting availability or performance. Autonomous Database handles creating the database, as well as the following maintenance tasks: Backing up the database Patching the database Upgrading the database Tuning the database. References:
https://www.youtube.com/watch?v=KKDLIjy2yJM&list=PLKCk3OyNwIzuHYigVbdtDOZOfChcotfj2&index
=7 https://severalnines.com/database-blog/autonomous-oracle-database-cheaper-than-free

Explanation
It is collection of related resources. Compartments are a fundamental component of Oracle Cloud Infrastructure for organizing and isolating your cloud resources. You use them to clearly separate resources for the purposes of measuring usage and billing, access (through the use of IAM Service policies), and isolation (separating the resources for one project or business unit from another). A common approach is to create a compartment for each major part of your organization. For more information, see Overview of the IAM Service and also Setting Up Your Tenancy.
To place a resource in a compartment, simply specify the compartment ID in the "Create" request object when initially creating the resource. For example, to launch an instance into a particular compartment, specify that compartment's OCID in the LaunchInstance request. You can't move an existing resource from one compartment to another.
To use any of the API operations, you must be authorized in an IAM policy. If you're not authorized, talk to an administrator. Ifyou're an administrator who needs to write policies to give users access, see Getting Started with Policies.

Reference: https://docs.oracle.com/en-
us/iaas/Content/Balance/Concepts/balanceoverview.htm#ariaid-title2