Oracle Cloud Infrastructure is a set of complementary cloud services that enable you to build and run a wide range of applications and services in a highly available hosted environment. Oracle Cloud Infrastructure offers high-performance compute capabilities (as physical hardware instances) and storage capacity in a flexible overlay virtual network that is securely accessible from your on-premises network.
Reference:
https://docs.cloud.oracle.com/en-us/iaas/Content/GSG/Concepts/baremetalintro.htm One of the major benefits of cloud computing is REDUCED TCO. Therefore, Increased TCO is the incorrect option.

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.
Reference:
https://docs.cloud.oracle.com/en-us/iaas/Content/General/Concepts/regions.htm

On an Exadata DB system, all databases share dedicated storage servers which include flash storage. By default, the databases are given equal priority with respect to these resources. The Exadata storage management software uses a first come, first served approach for query processing. If a database executes a major query that overloads I/O resources, overall system performance can be slowed down.
The I/O Resource Management (IORM) allows you to assign priorities to your databases to ensure critical queries are processed first when workloads exceed their resource allocations. You assign priorities by creating directives that specify the number of shares for each database. The number of shares corresponds to a percentage of resources given to that database when I/O resources are stressed.
Directives work together with an overall optimization objective you set for managing the resources. The following objectives are available:
1) Auto - Recommended. IORM determines the optimization objective and continuously and dynamically determines the optimal settings, based on the workloads observed, and resource plans enabled.
2) Balanced - For critical OLTP and DSS workloads. This setting balances low disk latency and high throughput. This setting limits disk utilization of large I/Os to a lesser extent than low latency to achieve a balance between good latency and good throughput.
3) High throughput - For critical DSS workloads that require high throughput.
4) Low latency - For critical OLTP workloads. This setting provides the lowest possible latency by significantly limiting disk utilization.

Customer and Oracle's responsibilities can be divided into the following areas:
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.
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.
Reference:
https://docs.cloud.oracle.com/en-us/iaas/Content/Security/Concepts/security_overview.htm

Oracle Cloud Infrastructure Marketplace is an online store that offers solutions specifically for customers of Oracle Cloud Infrastructure. In the Oracle Cloud Infrastructure Marketplace catalog, you can find listings for two types of solutions from Oracle and trusted partners: images and stacks. These listing types include different categories of applications. Also, some listings are free and others require payment.
Images are templates of virtual hard drives that determine the operating system and software to run on an instance. You can deploy image listings on an Oracle Cloud Infrastructure Compute instance. Marketplace also offers stack listings. Stacks represent definitions of groups of Oracle Cloud Infrastructure resources that you can act on as a group. Each stack has a configuration consisting of one or more declarative configuration files. With an image or a stack, you have a customized, more streamlined way of getting started with a publisher's software.
Reference:
https://docs.cloud.oracle.com/en-us/iaas/Content/Marketplace/Concepts/marketoverview.htm