This topic describes the physical and logical organization of Oracle Cloud Infrastructure resources.
About Regions and Availability Domains
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.
Oracle is adding multiple cloud regions around the world to provide local access to cloud resources for our customers. To accomplish this quickly, we have chosen to launch regions in new geographies with one availability domain.
As regions require expansion, we have the option to add capacity to existing availability domains, to add additional availability domains to an existing region, or to build a new region. The expansion approach in a particular scenario is based on customer requirements as well as considerations of regional demand patterns and resource availability.
Regions are independent of other regions and can be separated by vast distancesβacross countries or even continents. Generally, you would deploy an application in the region where it is most heavily used, because using nearby resources is faster than using distant resources. However, you can also deploy applications in different regions for these reasons:
To mitigate the risk of region-wide events such as large weather systems or earthquakes.
To meet varying requirements for legal jurisdictions, tax domains, and other business or social criteria.
Regions are grouped into realms . Your tenancy exists in a
single realm and can access all regions that belong to that realm. You cannot access
regions that are not in your realm. Currently, Oracle Cloud Infrastructure has multiple realms, including commercial, government, and dedicated realms.
The following table lists
the regions in the Oracle Cloud Infrastructure commercial realms :
To help balance capacity in data centers, Oracle Cloud Infrastructure randomizes availability domains by tenancy . For example, the availability domain labeled PHX-AD-1 for tenancyA might be a different data center than the one labeled PHX-AD-1 for tenancyB.
To track which availability domain corresponds to which data center for each tenancy, Oracle Cloud Infrastructure uses tenancy-specific prefixes for availability domain names. An example prefix is Uocm:. With this prefix, availability domain names are Uocm:PHX-AD-1, Uocm:PHX-AD-2, and so on.
To get the specific names of your tenancy's availability domains, use the ListAvailabilityDomains operation, which is available in the IAM API. You can also see the names when you use the Console to create an instance and choose which availability domain to create the instance in.
Fault Domains π
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.
To control the placement of your compute instances, bare metal DB system instances, or virtual machine DB system instances, you can optionally specify the fault domain for a new instance or instance pool at launch time. If you don't specify the fault domain, the system selects one for you. Oracle Cloud Infrastructure makes a best-effort anti-affinity placement across different fault domains, while optimizing for available capacity in the availability domain. To change the fault domain for a compute instance, edit the fault domain. To change the fault domain for a bare metal or virtual machine DB system instance, terminate it and launch a new instance in the preferred fault domain.
Use fault domains to do the following things:
Protect against unexpected hardware failures.
Protect against planned outages because of Compute hardware maintenance.
Trial, free tier, and pay-as-you-go tenancies are limited to one subscribed region. You
can request an increase to the limit for pay-as-you-go tenancies, see To request a subscribed region limit increase for more
information.
Universal monthly credit tenancies can subscribe to all publicly released commercial regions.
Requesting a Limit Increase to the Subscribed Region Count π
You can submit a request to increase the subscribed region count for your tenancies from within the Console. If you try to subscribe to a region beyond the limit for your tenancy, you'll be prompted to submit a limit increase request. Additionally, you can launch the request from the service limits page or at any time by clicking the link under the Help menu ().
Open the Help menu (), go to Support and click Request service limit increase.
Enter the following:
Primary Contact Details: Enter the name and email address of the person making the request. Enter one email address only. A confirmation will be sent to this address.
Service Category: Select Regions.
Resource: Select Subscribed region count.
Tenancy Limit: Specify the limit number.
Reason for Request: Enter a reason for your request. If your request is urgent or unusual, please provide details here.
Click Submit Request.
After you submit the request, it is processed. A response can take anywhere from a few minutes to a few days. If your request is granted, a confirmation email is sent to the address provided in the primary contact details.
If we need additional information about your request, a follow-up email is sent to the address provided in the primary contact details.
Service Availability Across Regions π
OCI offers its cloud services in all of its
public cloud regions and dedicated cloud regions. However, certain specialized or
emerging services are available only in select regions. For more information, see Service Availability.
Resource Availability π
The following sections list the resource types based on their availability: across regions, within a single region, or within a single availability domain.
Tip
In general: IAM resources are cross-region. DB Systems, instances, and volumes are specific to an availability domain. Everything else is regional. Exception: Subnets were originally designed to be specific to an availability domain. Now, you can create regional subnets, which are what Oracle recommends.
Cross-Region Resources π
API signing keys
compartments
detectors (Cloud Guard; regional to reporting region)
dynamic groups
federation resources
groups
managed lists (Cloud Guard)
network sources
policies (IAM and Zero Trust Packet Routing
responders (Cloud Guard; regional to reporting region)
buckets: Although buckets are regional resources, they can be accessed from any location if you use the correct region-specific Object Storage URL for the API calls.