The billing for an elastic pool consists of only compute resources, that is ECPU usage, and all compute usage is charged to the Autonomous Database instance that is the pool leader. Any billing for storage usage is charged separately to individual Autonomous Database instances, independent of whether the instance is in an elastic pool.

An elastic pool allows you to consolidate your Autonomous Database instances in terms of their compute resource billing. You can think of an elastic pool like a mobile phone service “family plan”, except this applies to your Autonomous Database instances. Instead of paying individually for each database, the databases are grouped into a pool in which one instance, the leader, is charged for the compute usage associated with the entire pool.

Using an elastic pool you are able to provision up to four times the number of ECPUs, over your selected pool size, and you can provision database instances that are in the elastic pool with as little as 1 ECPU per database instance. Outside of an elastic pool the minimum number of ECPUs per database instance is 2 ECPUs. For example, with a pool size of 128 you can provision 512 Autonomous Database instances (when each instance has 1 ECPU). In this example you are billed for the pool size compute resources, based on the pool size of 128 ECPUs, while you have access to 512 Autonomous Database instances. In contrast, when you individually provision 512 Autonomous Database instances without using an elastic pool you are required to allocate a minimum of 2 ECPUs for each Autonomous Database instance, and in this example you would pay for 1024 ECPUs. Using an elastic pool provides up to 87% compute cost savings.

After you create an elastic pool, the total ECPU usage for a given hour is charged to the Autonomous Database instance that is the pool leader. With the exception of the pool leader, individual Autonomous Database instances that are pool members are not charged for ECPU usage while they are members of an elastic pool.

Elastic pool billing is as follows:

• If the total aggregated peak ECPU utilization is equal to or below the pool size for a given hour, you are charged for the pool size number of ECPUs (one times the pool size).

  After an elastic pool is created ECPU billing continues at a minimum of one times the pool size rate, even when databases that are part of the pool are stopped. This applies to pool member databases and to the pool leader.

  In other words, if the aggregated peak ECPU utilization of the pool is less than or equal to the pool size for a given hour, you are charged for the pool size number of ECPUs (one times the pool size). This represents up to 87% compute cost savings over the case in which these databases are billed separately without using elastic pools.

• If the aggregated peak ECPU utilization of the pool leader and the members exceeds the pool size at any point in time in a given billing hour:

  • Aggregated peak ECPU utilization of the pool is equal to or less than two times of the pool size number of ECPUs: For usage that is greater than one times the pool size number of ECPUs and up to and including two times the number of ECPUs in a given billing hour: Hourly billing is two times the pool size number of ECPUs.

    In other words, if the aggregated peak ECPU utilization of the pool exceeds the pool size, but is less than or equal to two times the pool size for a given hour, you are charged for twice the pool size number of ECPUs (two times the pool size). This represents up to 75% compute cost savings over the case in which these databases are billed separately without using elastic pools.

  • Aggregated peak ECPU utilization of the pool is equal to or less than four times the pool size number of ECPUs: For usage that is greater than two times the pool size number of ECPUs and up and including to four times the pool size number of ECPUs in a given billing hour: Hourly billing is four times the pool size number of ECPUs.

    In other words, if the aggregated peak ECPU utilization of the pool exceeds twice the pool size for a given hour, you are charged for four times the pool size number of ECPUs (four times the pool size). This represents up to 50% compute cost savings over the case in which these databases are billed separately without using elastic pools.

  For example, consider an elastic pool with a pool size of 128 ECPUs and a pool capacity of 512 ECPUs:

  • Case-1: The aggregated peak ECPU utilization of the pool leader and the members is 40 ECPUs between 2:00pm and 2:30pm, and 128 ECPUs between 2:30pm and 3:00pm.

    The elastic pool is billed 128 ECPUs, one times the pool size, for this billing hour (2-3pm). This case applies when the peak aggregated ECPU usage of the elastic pool for the billing hour is less than or equal to 128 ECPUs.

  • Case-2: The aggregated peak ECPU utilization of the pool leader and the members is 40 ECPUs between 2:00pm and 2:30pm, and 250 ECPUs between 2:30pm and 3:00pm.

    The elastic pool is billed 256 ECPUs, two times the pool size, for this billing hour (2-3pm). This case applies when the peak aggregated ECPU usage of the elastic pool for the billing hour is less than or equal to 256 ECPUs and greater than 128 ECPUs.

  • Case-3: The aggregated peak ECPU utilization of the pool leader and the members is 80 ECPUs between 2:00pm and 2:30pm, and 509 ECPUs between 2:30pm and 3:00pm.

    The elastic pool is billed 512 ECPUs, four times the pool size, for this billing hour (2-3pm). This case applies when the peak aggregated ECPU usage of the elastic pool for the billing hour is less than or equal to 512 ECPUs and greater than 256 ECPUs.

See How to Achieve up to 87% Compute Cost Savings with Elastic Resource Pools on Autonomous Database for more details.

SELECT billed_quantity FROM OCI_USAGE_DATA
   WHERE resource_name='PIC_ADBS_DB_ECPU_PEAK' and
                    resource_id=OCID_of_the_pool_member and
                    interval_usage_start=start_time and
                    interval_usage_end=end_time

SELECT billed_quantity FROM OCI_USAGE_DATA
   WHERE resource_name='PIC_ADBS_DB_ECPU_PEAK' and
                    resource_id=OCID_of_the_pool_leader and
                    interval_usage_start=start_time and
                    interval_usage_end=end_time

SELECT billed_quantity FROM OCI_USAGE_DATA
   WHERE resource_name='PIC_ADBS_ELASTIC_POOL_DB_ECPU' and
                    resource_id=OCID_of_the_pool_leader and
                    interval_usage_start=start_time and
                    interval_usage_end=end_time

The Autonomous Database instance that creates an elastic pool is the pool leader. Autonomous Database instances that are added to an existing pool are pool members. Depending on your role, either leader or member, you can perform operations on an elastic pool.

Shows the steps to join an existing elastic pool.

1. On the Autonomous Database Details page select Manage resource allocation.

   Verify that Compute auto scaling is disabled.

   If Compute auto scaling is selected, disable Compute auto scaling:

   1. In the Manage resource allocation area, deselect Compute auto scaling.
   2. Click Apply.

      The Lifecycle state changes to Scaling in Progress. After some time the Lifecycle state changes to Available.

   3. On the Autonomous Database Details page select Manage resource allocation to display the Manage resource allocation area.
2. In the Manage resource allocation area, click Show advanced options to show the advanced options.
3. Select Enable elastic pool.
4. Select Join an existing elastic pool.
5. In the Select pool leader in compartment field choose a pool leader in a compartment.
   1. Use the compartment shown or click Change Compartment to select a different compartment.
   2. Select a pool leader from the list of available pool leaders in the selected compartment.
6. Click Apply to add the instance to the elastic pool.

Shows the steps for the pool leader to change the elastic pool shape for an existing elastic pool.

1. On the Autonomous Database Details page select Manage resource allocation to display the Manage resource allocation area.
2. In the Pool ECPU count field, select a value that is different than the current value

   By default each instance in an elastic pool is automatically assigned a maintenance window. By selecting a Pool ECPU count that is 1024 greater, you have the option of assigning a custom 2-hour maintenance window during which the leader and all elastic pool members are patched together. To select a custom maintenance window for your elastic pool, file a Service Request at Oracle Cloud Support.

   See About Scheduled Maintenance and Patching for more information.

3. Click Apply.

   When you click Apply, the Lifecycle state changes to Scaling in Progress. After the Lifecycle state changes to Available the changes apply immediately.

An elastic pool leader can remove pool members from an elastic pool.

1. On the Autonomous Database Details page, under Resources, click Elastic pool members.

   This shows the Elastic pool members area, with a list showing details for each instance that is an elastic pool member.

2. Click at the end of a row for an instance you want to remove and in the drop down list select Remove from pool.

   This shows the Remove from pool confirmation dialog.

3. Click Leave to confirm.

   When you click Leave, the Lifecycle state changes to Scaling in Progress. After the Lifecycle state changes to Available the changes apply immediately.

Provides information about resources when a member or the leader leaves an elastic pool.

• When a pool member or the leader leaves an elastic pool, auto scaling is disabled. After leaving the elastic pool you can enable auto-scaling for the instance.

• When a pool member leaves an elastic pool, the elastic pool has more resources available. For example, if the elastic pool were fully allocated up to the pool capacity, and an instance with 10 ECPUs leaves the pool, the elastic pool would have 10 available ECPUs.

• Billing for an Autonomous Database instance that leaves an elastic pool returns to individual instance billing, based on the compute and storage resources that the individual instance uses:

  • If a pool member with 2 ECPUs or more leaves the pool, the individual instance's ECPU allocation remains and the instance is billed for that number of ECPUs.

  • If a pool member with 1 ECPU leaves the pool, the ECPU allocation is automatically set to 2 ECPUs and the instance is billed for 2 ECPUs going forward, unless it's scaled up.