OCI Overview and Key Concepts

Realm: is a logical collection of regions. Realms are isolated from each other and do not share any data. Your tenancy exists in a single realm and has access to the regions that belong to that realm. Oracle Cloud Infrastructure currently offers a realm for commercial regions and two realms for government cloud regions: FedRAMP authorized and IL5 authorized.


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 available domains.  Bu default Home region, in which you have signed up is subscribed, and to use another region.

All services except few AD-based services are regional.

Availability domains

Availability domains are isolated from each other, fault-tolerant, and very unlikely to fail simultaneously or be impacted by the failure of another availability domain.

AD based Services

  • DB systems (Oracle Database service)
  • ephemeral public IPs
  • instances: They can be attached only to volumes in the same availability domain.
  • subnets: When you create a subnet, you choose whether it is regional or specific to an availability domain. Oracle recommends using regional subnets.
  • volumes: They can be attached only to an instance in the same availability domain.

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 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.

CrossRegional / Tenency Based Service

  • IAM resources are cross-region.
  • Traffic Management and Health Checkup


A compartment should be thought of as a logical group and not a physical container. When you begin working with resources in the Console, the compartment acts as a filter for what you are viewing. By default there is a root compartment.

  • Create compartment quota policies. When setting a quota that has a scope of availability domain (AD), the quota is allocated to each AD unless you specify an AD in the policy. Regional quotas apply to each region.
  • The following resource can be managed from quota policies
    • Compute Shapes
    • Custom Images
    • Instance Configuration
    • Instance Pools
    • Auto Scaling

Resource Identifier


ocid1: The literal string indicating the version of the Oracle


Cost Management

  • Payment Model
    • Pay As you go , Monthly Billing
    • Yearly Contract reservation
    • Universal Credit
  • Must be a member of Admin Group
  • Cost can be tracked on basis of cost tracking tags, date or compratements


  • Budget can be setup on actual usage or forecast
  • Track actual and forecast spending
  • Set Alerts on predefined thresholds, get notified
  • Must be allowed to use “usage-budgets”
  • All created in Root Compartment
  • 4 levels of Budget access, Inspect, Read, Use, Manage

Usage Reports

  • CSV file with 1 record per resource per hour
  • Automatically generated daily
  • Contains 24 hours of usage data
  • Retained for 1 year

Leave a Reply

Your email address will not be published. Required fields are marked *