ApsaraDB RDS:Change the scaling range of computing resources (RCUs)

How it works

RDS SQL Server Serverless instances measure performance in RCUs. A Serverless instance automatically scales RCUs up or down based on the actual workload. This scaling occurs within the minimum and maximum RCU range that you set.

RCU scaling depends on the instance's CPU utilization, memory pressure, and average active sessions (AAS). When any of these metrics reaches the scale-out threshold, the RCU count automatically increases within minutes. When all three metrics are below the scale-in threshold, the RCU count automatically decreases within minutes.

Scenarios

• If you expect a traffic spike that could increase the load and cause performance jitter, you can increase the minimum RCU value to prevent this issue.

• To save costs, you can lower the maximum RCU value. However, this operation might affect instance performance, so proceed with caution.

Impacts

• Changes to the RCU range of a Serverless instance take effect in about one minute.

• Modifying the maximum or minimum RCU value has the following effects:

  • Modifying the maximum RCU value

    • If the current RCU count is lower than the new maximum value, the RCU count does not change.

    • If the current RCU count is higher than the new maximum value, the RCU count immediately drops to the new maximum value when the configuration takes effect.

    • If the current maximum RCU value is insufficient for your business needs, the RCU count immediately increases to the new maximum value when the configuration takes effect.

      For example, a traffic spike occurs. The current maximum RCU value is 6 and is insufficient. You change the maximum value to 8. The system immediately increases the RCU count to 8 when the change takes effect.

  • Modifying the minimum RCU value

    • If the current RCU count is higher than the new minimum value, the RCU count does not change.

    • If the current RCU count is lower than the new minimum value, the RCU count immediately increases to the new minimum value when the change takes effect.

Billing

Changing the RCU scaling range does not incur fees. RCU fees are calculated based on actual usage.

Procedure

1. Go to the RDS Instances page. In the top navigation bar, select a region. Then, click the ID of the target instance.

2. On the Basic Information page, find the Configuration Information section and click Adjust Elastic Settings.

3. In the dialog box that appears, set the Minimum and Maximum values for the Resource Scaling Range (RCU).

   Note

   The RCU value can be set to an integer from 2 to 16. Set the value as needed.

4. Click OK.

References

• For information about how to increase the storage space of your Serverless instance, see Increase storage space.

• To save costs, you can pause a Serverless instance when it is not needed. For more information, see Manually pause or start an instance and Billing for different instance statuses.

• When you no longer need a Serverless instance, you can release it. For more information, see Release an instance.

• RCU scaling usually takes seconds. In rare cases, cross-machine scaling may take 3 to 5 minutes. If you require high stability during specific periods, you can schedule the RCU configuration for a Serverless instance to increase the RCU count in advance.

• To modify the RCU range of a Serverless instance using an API operation, see ModifyDBInstanceSpec.