Oracle Cloud Infrastructure Documentation

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 several 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.

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 is unlikely to impact the availability of the others.

All the availability domains in a 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 customer premises, and to build replicated systems in multiple availability domains for both high-availability and disaster recovery.

Regions are completely independent of other regions and can be separated by vast distances—across countries or even continents. Generally, you would deploy an application in the region where it is most heavily used, since using nearby resources is faster than using distant resources. However, you can also deploy applications in different regions to:

  • mitigate the risk of region-wide events, such as large weather systems or earthquakes
  • meet varying requirements for legal jurisdictions, tax domains, and other business or social criteria
Region Location Region Name Region Key
Phoenix, AZ metropolitan area us-phoenix-1 PHX
Ashburn, VA us-ashburn-1 IAD
Frankfurt, Germany eu-frankfurt-1 FRA
London, United Kingdom uk-london-1 LHR

To subscribe to a region, see Managing Regions.


Your Tenancy's Availability Domain Names

Oracle Cloud Infrastructure randomizes the availability domains by The root compartment that contains all of your organization's compartments and other Oracle Cloud Infrastructure cloud resources. to help balance capacity in the data centers. For example, the availability domain labeled PHX-AD-1 for tenancyA may be a different data center than the one labeled PHX-AD-1 for tenancyB. To keep track of which availability domain corresponds to which data center for each tenancy, Oracle Cloud Infrastructure uses tenancy-specific prefixes for the availability domain names. For example: the availability domains for your tenancy are something like 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 launch an instance and choose which availability domain to launch the instance into.

Fault Domains

A fault domain is a grouping of hardware and infrastructure within an availability domain. Each availability domain contains three fault domains. Fault domains let you distribute your instances so that they are not on the same physical hardware within a single availability domain. A hardware failure or Compute hardware maintenance that affects one fault domain does not affect instances in other fault domains.

To control the placement of your instances, you can optionally specify the fault domain for a new instance at launch time. If you do not specify the fault domain, the system selects one for you. To change the fault domain for an instance, terminate it and launch a new instance in the preferred fault domain.

Use fault domains to:

  • Protect against unexpected hardware failures
  • Protect against planned outages due to Compute hardware maintenance

See Fault Domains in Best Practices for Your Compute Instance for recommendations when using fault domains.

Resource Availability

The following sections list the resource types based on their availability: global across regions, within a single region, or within a single availability domain.


In general: IAM resources are global. DB Systems, instances, volumes, and subnets are specific to an availability domain. Everything else is regional.

Global Resources

  • API signing keys
  • compartments
  • dynamic groups
  • encryption keys
  • federation resources
  • groups
  • key vaults
  • policies
  • tag namespaces
  • tag keys
  • users

Regional Resources

  • 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.
  • clusters
  • customer-premises equipment (CPE)
  • DHCP options sets
  • dynamic routing gateways (DRGs)
  • images
  • internet gateways
  • load balancers
  • local peering gateways (LPGs)
  • NAT gateways
  • node pools
  • repositories
  • reserved public IPs
  • route tables
  • security lists
  • service gateways
  • virtual cloud networks (VCNs)
  • volume backups: They can be restored as new volumes to any availability domain within the same region in which they are stored.

Availability Domain-Specific Resources

  • DB Systems
  • ephemeral public IPs
  • instances: They can be attached only to volumes in the same availability domain.
  • subnets
  • volumes: They can be attached only to an instance in the same availability domain.