About Oracle Cloud Infrastructure Terminology

Before you plan your deployment on Oracle Cloud Infrastructure, become familiar with the Oracle Cloud Infrastructure terminology.

Term	Definition
Availability domains and regions	Oracle Cloud Infrastructure is physically 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 several availability domains. Oracle Cloud Infrastructure resources are either region-specific, such as a virtual cloud network, or availability domain-specific, such as a compute instance. Availability domains are isolated from each other, are fault tolerant, and are unlikely to fail simultaneously and are unlikely to be affected by the failure of another availability domain. When you configure your cloud services, use multiple availability domains to ensure high availability and to protect against resource failure. Be aware that some resources must be created in the same availability domain, such as an instance and the storage volume attached to it.
Database system	The database service lets you quickly launch an Oracle database system and create one or more databases on it. You have full access to the features and operations available with Oracle Database, but Oracle owns and manages the infrastructure.
Dynamic routing gateway (DRG)	A software-defined router that provides a path for private traffic between your virtual cloud network (VCN) and your data center’s network. You can use it with the Internet Protocol Security (IPSec) virtual private network (VPN) connection and an on-premises router to create a site-to-site VPN.
Fault domain	A fault domain is a grouping of hardware and infrastructure within an availability domain. Fault domains enable you to distribute your instances so that they are not on the same physical hardware within a single availability domain. As a result, a hardware failure or hardware maintenance that affects one fault domain does not affect instances in other fault domains.
File storage service (FSS)	Use Oracle Cloud Infrastructure File Storage service to provide the shared disk resource for JD Edwards EnterpriseOne shared application-tier file system. This service supports the Network File System version 3.0 (NFSv3) protocol and the Network Lock Manager (NLM) protocol for file locking functionality.
Internet gateway	A software-defined router that provides a path for network traffic from your virtual cloud network (VCN) to the internet.
Load balancer	A load balancer improves resource utilization, facilitates scaling, and helps ensure high availability. Oracle Cloud Infrastructure Load Balancing provides automated traffic distribution from one entry point to multiple servers that are reachable from your VCN. The service offers a load balancer with your choice of a public or private IP address, and provisioned bandwidth.
Network Address Translation (NAT) gateway	A NAT gateway provides cloud resources (without public IP addresses) access to the Internet without exposing those resources to incoming Internet connections. Instances in a private subnet don't have public IP addresses. With a NAT gateway, instances can initiate connections to the Internet and receive responses, but they can’t receive inbound connections initiated from the Internet. NAT gateways are highly available and support TCP, UDP, and ICMP ping traffic.
Oracle Cloud Infrastructure Compute instance	An Oracle Cloud Infrastructure Compute instance is a compute host running in the cloud. Oracle Cloud Infrastructure offers both Bare Metal and Virtual Machine instances. Bare metal compute instance gives you dedicated physical server access for highest performance and strong isolation. A Virtual Machine (VM) is an independent computing environment that runs on top of physical bare metal hardware. Virtualization makes it possible for you to run multiple VMs that are isolated from each other.
Oracle Cloud Infrastructure FastConnect	Oracle Cloud Infrastructure FastConnect provides an easy way to create a dedicated, private connection between your data center and Oracle Cloud Infrastructure. Oracle Cloud Infrastructure FastConnect provides higher-bandwidth options, and a more reliable and consistent networking experience compared to Internet-based connections.
Security list	A common set of stateful firewall rules that are associated with a subnet and applied to all instances launched in the subnet. Security lists contain ingress and egress rules to filter traffic at the subnet level and contain information about which communication ports allow data transfer.
Service gateway	A service gateway lets resources in your virtual cloud network (VCN) access public Oracle Cloud Infrastructure services such as Object Storage, but without using an internet gateway or NAT. Any traffic from your VCN that is destined for one of the supported public services uses the instance's private IP address for routing, travels over the Oracle Cloud Infrastructure network fabric, and never traverses the internet.
Subnet	A section of a VCN’s IP address range that provides logical isolation for resource groups. You create a subnet by subdividing the VCN's address range. When you create a subnet in Oracle Cloud Infrastructure, you specify a contiguous IPv4 Classless Inter-Domain Routing (CIDR) block for the subnet. The subnet's CIDR block must fall within the VCN's CIDR block. A subnet can’t span availability domains. You assign a subnet to one availability domain. When you launch an instance in a subnet, the instance's private IP address is derived from the subnet's CIDR block. When you create a subnet, you can specify whether the access type is private or public. A subnet is created with public access by default, which means that the instances in the subnet can be allocated a public IP address. However, instances launched in a subnet with private access aren’t allowed to have public IP addresses, which ensure that these instances have no internet access.
Virtual cloud network (VCN)	A virtual cloud network is a virtual version of a traditional network—including subnets, route tables, and gateways—that your instances run on. A VCN resides in a single region but can cross multiple availability domains. You can define subnets for a VCN in different availability domains, but the subnet itself must belong to a single availability domain. You must set up at least one VCN before you can launch instances. You can configure the VCN with an optional internet gateway to handle public traffic, and an optional IPSec VPN connection to securely extend your on-premises network. When you create your VCN, you assign a contiguous IPv4 CIDR block of your choice. You can create multiple VCNs with overlapping IP address ranges. However, if you intend to connect your VCN to your on-premises network through an IPSec VPN connection, ensure the IP address ranges don’t overlap.