What is a Region?
In OCI terms, a region is a single localized geographical area where Oracle has deployed Oracle Cloud Infrastructure.
Each region is wholly independent of other regions and can be thousands of miles apart from other regions.
Generally, you deploy a workload in the region where it is going to be most heavily used. This is 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.
Home Region
When you sign up for Oracle Cloud Infrastructure, Oracle creates a tenancy for you in one region. This is your home region and cannot be changed. Your home region is where your identity resources are defined.
When you subscribe to another region, your identity resources are available in the new region. However, the master definitions reside in your home region and can only be changed there.
Resources that you can create and update only in the home region are:
- Users
- Groups
- Policies
- Compartments
- Dynamic groups
- Federation resources
Although your tenancy can be subscribed to multiple regions, most instances of cloud resources are region-specific. i.e. they cannot be deployed across regions. They can be accessed from resources in multiple regions, but they can only be deployed and administered in one.
You can maintain control and governance in your tenancy for the use of non-home regions and the services and resources within them. For example;
- You can use policies to restrict access to specific regions for specific user Groups
- You can impose service limits on specific OCI Services at a regional level
OCI Realms
Regions are grouped into realms.
A realm enables Oracle to provide defined levels of service across regions that meet the specific needs of different organization classifications. These needs typically relate to heightened levels of security and separation.
For the most part, there are two classes of realm;
- Realms that meet the needs of commercial organizations
- All commercial regions belong to the same realm; OC1
- Realms that meet the needs of governmental organizations
- US Government: FedRAMP Authorized
- US Government: IL5 Authorized
- UK Government
Your tenancy can access services and deploy workloads across all regions within the same realm, but it cannot reach across realms.
Regional Services
All Oracle Cloud Infrastructure regions offer core infrastructure services, including the following:
- Compute: Compute (Intel-based bare metal & VM, DenseIO & Standard), Container Engine for Kubernetes, Container Registry, Artifact Registry
- Storage: Block Volume, File Storage, Object Storage, Archive Storage
- Networking: Virtual Cloud Network, Load Balancing, FastConnect (specific partners as available and requested)
- Database: Database, Exadata Cloud Service, Autonomous Data Warehouse, Autonomous Transaction Processing
- Edge: DNS
- Platform: Audit, Identity and Access Management, Monitoring, Notifications, Tagging, Work Requests
- Security: Vault
Services in addition to those listed above are made regionally available according to several considerations, including; customer demand, regulatory compliance, and resource availability.
When services are unavailable in your home region you can use cloud services in other regions with very effective results. Oracle Cloud Infrastructure’s low latency interconnect backbone makes this possible. Make sure you consider any applicable data residency requirements before doing so.
Availability & Fault Domains
Availability domains and fault domains are designed to deliver physical resilience.
- Availability domains protect against systemic physical failure within an OCI data centre.
- Fault domains protect against individual physical component failure within an OCI deployment.
Tip:
Benefitting from either of these two protection mechanisms requires detailed design and planning with regards to deployment and resource placement.
What is an Availability Domain?
An availability domain is one or more data centers within an Oracle Region. 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 by a low latency, high bandwidth network. The high-speed connectivity makes it possible to build replicated systems, in multiple availability domains, for both high-availability and disaster recovery.
Most regions have one availability domain. The exceptions to this are; Germany Central (Frankfurt), UK South (London), US East (Ashburn) and US West (Phoenix). These regions have three availability domains.
What is a Fault Domain?
A fault domain is a grouping of hardware and infrastructure within an availability domain. Each availability domain contains three fault domains. 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.
Tip:
To provide resilience for clustered resources in regions with one availability domain, we recommend making explicit use of fault domains.
The Resilience topic of the Cloud Foundation contains more information on how to make the best use of availability domains and fault domains. The reason for referencing them in the Control & Governance topic is that the number of availability domains may influence your selection of a region for your Home region and for specific OCI workloads/applications.
Selecting a Region for Deployment
Important:
Guidance for selecting your Home Region
Selecting a region for the deployment of an OCI application or workload must take into consideration the following;
- Does the region meet the data residency requirements of my organization?
- Are all the OCI services required available in the region?
- Does the region offer the number of availability domains required to meet RTO/RPO objectives?
- Is the region sufficiently geographically close to the majority of users?
- Is the region shared with, or geographically close to, dependent or integrated applications?
In general: IAM resources are cross-region. DB Systems, instances, and volumes are specific to an availability domain. Everything else is regional (except cross-regional Subnets).