1. Best practices for designing reliable and resilient cloud topologies
  2. Manage Your Service Limits

Manage Your Service Limits

Understand, monitor, and manage your tenancy's service limits and compartment quotas. Service limits are resource allowances that limit what resources you can use in your tenancy. They are established when you create your tenancy, but can be changed on request. Compartment quotas are policies that allow administrators to allocate resources to specific compartments with a high level of flexibility.

Understand the Default Service Limits of Your Tenancy

Enterprise Architect, Cloud Architect, Infrastructure Lead

Typically, the service limits associated with your tenancy are established when you sign up for Oracle Cloud Infrastructure (OCI).

If you didn't establish limits with your Oracle sales representative or if you signed up through the Oracle Store, then default or trial limits are set for your tenancy. Use the OCI Console or API to view your service limits.

OCI is hosted in regions and availability domains. Regions are localized geographic areas, and availability domains are one or more data centers within a region. Each resource has a defined limit and scope. The scope of service limits is either regional or availability domain specific. In some cases, the scope is defined by another service. For example, only one NAT Gateway resource is allowed per virtual cloud network. The scope of service limits for a NAT Gateway is virtual cloud network.

Follow these best practices to determine the service limits of your tenancy:

  1. Identify your Oracle Cloud Infrastructure regions based on your application, latency, and disaster recovery requirements.
  2. Identify the services that your applications require.

To determine your requirements, review the application architecture, infrastructure code, or on-premises deployment and follow these best practices:

  1. Review the default limits and scope for your required services. For example, per availability domain, per region, or per tenant. Some services have additional limits.
  2. Identify which default service limits require an increase.
  3. Understand the capacity that is required to run your application at peak load, and ensure your limits allow resiliency in the event of the failure of an availability domain.
Service Limits serve the following purposes:
  • Allow you to protect yourself from unexpected consumption by ensuring your tenancy can only use the resources you want.
  • Inform Oracle of the resources you need to run your workload so those resources are always available to you.
You are only charged for resources you actually use, regardless of your service limits.

Monitor and Manage Your Service Limits

Cloud Architect, Infrastructure Lead

Evaluate the use of Oracle Cloud Infrastructure services based on your application. Leave room for growth and expansion. Keep track of your current usage and monitor growth.

  • Use the OCI Console or Service Limits API to capture your current resource utilization and total service limits for your tenancy. For example, how many compute instances you're using per availability domain and how much room you have to grow in that availability domain and region.

  • Request an increase in the service limit for a resource, if required. Keep a record and track the request. After receiving confirmation, go to the OCI Console or Service Limits API to validate the service limit.

Set Compartment Quotas

Cloud Architect, Infrastructure Lead

Administrators use policy statements to create compartment quotas. The quotas control how resources are consumed in your cloud compartments.
  1. Identify services and their quota requirements for each compartment, based on your compartment structure. Quotas set at a parent compartment level, limit resource use for that compartment and all of its children. When setting quotas for a parent compartment, remember to include the usage in child compartments.
  2. Identify the scope of the compartment quotas as availability domain, regional, or global.
  3. 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.
  4. Set an upper boundary to prevent errant configurations from creating request storms that create unlimited resources.

Be Aware of Fixed Service Limits

Cloud Architect, Infrastructure Lead

Be aware that some resources have fixed, unchangeable service limits.

Identify those that might impact your applications and make appropriate adjustments to the architecture. For example, you can attach a maximum of 5 security lists to a single subnet. To overcome this limit, you can adjust your architecture to use network security groups in addition to security lists.

Factor Failover Usage in Your Service Limits

Cloud Architect, Infrastructure Lead

Ensure that you factor in a sufficient gap between the current service limit and the maximum usage to accommodate failover.

When a resource fails, it might still be counted against limits until it is successfully terminated. Ensure that your limits cover the overlap of all failed resources with replacements before the failed resources are terminated. You should consider an availability domain failure when calculating this gap.

  1. Understand your reliability and availability scenario, and how you are making your architecture resilient enough to accommodate that. Typically, availability is in the form of 'number of 9s'.
  2. Understand your deployment patterns, such as Blue/Green, rollover, or canary.
  3. Have an appropriate buffer on your service limits for failover.
  4. Leave appropriate room for future growth and expansion.

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