Explanation
When creating a compartment, you must provide a name for it (maximum 100 characters, including letters, numbers, periods, hyphens, and underscores) that is unique within its parent compartment. You must also provide a description, which is a non-unique, changeable description for the compartment, from 1 through 400 characters. Oracle will also assign the compartment a unique ID called an Oracle Cloud ID.
You can create subcompartments in compartments to create hierarchies that are six levels deep.

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.
Regions are independent of other regions and can be separated by vast distances-across countries or even continents.
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.
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.

Explanation
Oracle Cloud Infrastructure's security approach is based on seven core pillars. Each pillar has multiple solutions designed to maximize the security and compliance of the platform and to help customers to improve their security posture.
High Availability: Offer fault-independent data centers that enable high-availability scale-out architectures and are resilient against network attacks, ensuring constant uptime in the face of disaster and security attack.
Customer Isolation: Allow customers to deploy their application and data assets in an environment that commits full isolation from other tenants and Oracle's staff.
Data Encryption: Protect customer data at-rest and in-transit in a way that allows customers to meet their security and compliance requirements with respect to cryptographic algorithms and key management.
Security Controls: Offer customers effective and easy-to-use application, platform, and network security solutions that allow them to protect their workloads, have a secure application delivery using a global edge network, constrain access to their services, and segregate operational responsibilities to reduce the risk associated with malicious and accidental user actions.
Visibility: Offer customers comprehensive log data and security analytics that they can use to audit and monitor actions on their resources, allowing them to meet their audit requirements and reduce security and operational risk.
Secure Hybrid Cloud: Enable customers to use their existing security assets, such as user accounts and policies, as well as third-party security solutions, when accessing their cloud resources and securing their data and application assets in the cloud.
Verifiably Secure Infrastructure: Follow rigorous processes and use effective security controls in all phases of cloud service development and operation. Demonstrate adherence to Oracle's strict security standards through third-party audits, certifications, and attestations. Help customers demonstrate compliance readiness to internal security and compliance teams, their customers, auditors, and regulators.

Explanation
Oracle Cloud Infrastructure offers best-in-class security technology and operational processes to secure its enterprise cloud services. However, for you to securely run your workloads in Oracle Cloud Infrastructure, you must be aware of your security and compliance responsibilities. By design, Oracle provides security of cloud infrastructure and operations (cloud operator access controls, infrastructure security patching, and so on), and you are responsible for securely configuring your cloud resources. Security in the cloud is a shared responsibility between you and Oracle.
In a shared, multi-tenant compute environment, Oracle is responsible for the security of the underlying cloud infrastructure (such as data-center facilities, and hardware and software systems) and you are responsible for securing your workloads and configuring your services (such as compute, network, storage, and database) securely.
In a fully isolated, single-tenant, bare metal server with no Oracle software on it, your responsibility increases as you bring the entire software stack (operating systems and above) on which you deploy your applications.
In this environment, you are responsible for securing your workloads, and configuring your services (compute, network, storage, database) securely, and ensuring that the software components that you run on the bare metal servers are configured, deployed, and managed securely.
More specifically, your and Oracle's responsibilities can be divided into the following areas:
Identity and Access Management (IAM): As with all Oracle cloud services, you should protect your cloud access credentials and set up individual user accounts. You are responsible for managing and reviewing access for your own employee accounts and for all activities that occur under your tenancy. Oracle is responsible for providing effective IAM services such as identity management, authentication, authorization, and auditing.
Workload Security: You are responsible for protecting and securing the operating system and application layers of your compute instances from attacks and compromises. This protection includes patching applications and operating systems, operating system configuration, and protection against malware and network attacks. Oracle is responsible for providing secure images that are hardened and have the latest patches. Also, Oracle makes it simple for you to bring the same third-party security solutions that you use today.
Data Classification and Compliance: You are responsible for correctly classifying and labeling your data and meeting any compliance obligations. Also, you are responsible for auditing your solutions to ensure that they meet your compliance obligations.
Host Infrastructure Security: You are responsible for securely configuring and managing your compute (virtual hosts, containers), storage (object, local storage, block volumes), and platform (database configuration) services. Oracle has a shared responsibility with you to ensure that the service is optimally configured and secured. This responsibility includes hypervisor security and the configuration of the permissions and network access controls required to ensure that hosts can communicate correctly and that devices are able to attach or mount the correct storage devices.
Network Security: You are responsible for securely configuring network elements such as virtual networking, load balancing, DNS, and gateways. Oracle is responsible for providing a secure network infrastructure.
Client and Endpoint Protection: Your enterprise uses various hardware and software systems, such as mobile devices and browsers, to access your cloud resources. You are responsible for securing all clients and endpoints that you allow to access Oracle Cloud Infrastructure services.
Physical Security: Oracle is responsible for protecting the global infrastructure that runs all of the services offered in Oracle Cloud Infrastructure. This infrastructure consists of the hardware, software, networking, and facilities that run Oracle Cloud Infrastructure services.