Explanation/Reference: https://searchcloudcomputing.techtarget.com/definition/Infrastructure-as-a-Service-IaaS

Explanation
You can open a support service request with Oracle Support
To create a service request:
Go to My Oracle Support and sign in.
If you are not signed in to Oracle Cloud Support, click Switch to Cloud Support at the top of the page.
Click Create Service Request.
Select the following from the displayed menus:
Service Type: Select Oracle Cloud Infrastructure from the list.
Service Name: Select the appropriate option for your organization.
Problem Type: Select your problem type from the list.
Enter your contact information.
Enter a Description, and then enter the required fields specific to your issue. For most Oracle Cloud Infrastructure issues you need to include the OCID (Oracle Cloud Identifier) for each resource you need help with. See Locating Oracle Cloud Infrastructure IDs for instructions on locating these.

Explanation
Oracle Cloud Infrastructure is hosted in regions and availability domains. A region is a localized geographic area, and an availability domain is one or more data centers located within a region. A region is composed of one or more availability domains. Most Oracle Cloud Infrastructure resources are either region-specific, such as a virtual cloud network, or availability domain-specific, such as a compute instance. Traffic between availability domains and between regions is encrypted.
Availability domains are isolated from each other, fault tolerant, and very unlikely to fail simultaneously.
Because availability domains do not share infrastructure such as power or cooling, or the internal availability domain network, a failure at one availability domain within a region is unlikely to impact the availability of the others within the same region.
The availability domains within the same region are connected to each other by a low latency, high bandwidth network, which makes it possible for you to provide high-availability connectivity to the internet and on-premises, and to build replicated systems in multiple availability domains for both high-availability and disaster recovery.
A fault domain is a grouping of hardware and infrastructure within an availability domain. Each availability domain contains three fault domains. Fault domains provide anti-affinity: they let you distribute your instances so that the instances are not on the same physical hardware within a single availability domain. A hardware failure or Compute hardware maintenance event that affects one fault domain does not affect instances in other fault domains. In addition, the physical hardware in a fault domain has independent and redundant power supplies, which prevents a failure in the power supply hardware within one fault domain from affecting other fault domains.