Database Autonomy Service (DAS) provides the automatic performance scaling feature for CPU specifications of database instances. DAS can automatically scale up your database instance to handle traffic spikes during peak hours and ensure the stability of your business. DAS monitors the CPU utilization of your database instance in real time. If the CPU utilization decreases within a specified observation window, DAS automatically scales down the database instance. This topic describes how to enable the automatic performance scaling feature.
Prerequisites
- An ApsaraDB RDS for MySQL High-availability Edition instance that uses standard or
enhanced SSDs or a PolarDB for MySQL cluster of the Cluster Edition is connected to
DAS.
Note The automatic performance scaling feature is not supported for ApsaraDB RDS for MySQL instances whose instance types are phased out. If the instance type of your ApsaraDB RDS for MySQL instance is phased out, you must change the instance type of the instance before you can enable the automatic performance scaling feature. For information about how to change the instance type of an ApsaraDB RDS for MySQL instance, see Change the specifications of an ApsaraDB RDS for MySQL instance.
- The autonomy service is enabled for the database instance. For more information, see Autonomy center.
- Your Alibaba Cloud account has sufficient balance to pay for scaled-up resources.
- A DAS-linked role is created. For more information, see AliyunServiceRoleForDAS role.
Note If you have not created a RAM role that is linked to DAS, DAS can automatically create a service-linked role when you enable the automatic performance scaling feature.
Process of automatic scale-up

- For an ApsaraDB RDS for MySQL instance, DAS does not automatically scale down the instance after the CPU utilization decreases to the specified threshold. You can enable the event subscription service to subscribe to notifications of scale-down suggestions. If the CPU utilization of your database instance is lower than 30% for longer than 99% of the observation window, DAS sends messages to suggest you to scale down the database instance. By default, an observation window is set to 30 minutes. You must manually scale down the database instance. For more information, see Change the specifications of an ApsaraDB RDS for MySQL instance.
- For a PolarDB for MySQL cluster, if the CPU utilization is lower than 30% for longer than 99% of the quiescent period after you select Automatic Scale-down/in, a scale-down is triggered when the quiescent period ends. The PolarDB cluster is scaled down to the original specifications in small decrements.
Pricing
- For an ApsaraDB RDS for MySQL instance:
You are charged based on the new instance specifications after the automatic scale-up. The price for a scale-up varies based on the instance configurations, such as the region and the new instance specifications. For more information, visit the ApsaraDB RDS buy page.
- For a PolarDB for MySQL cluster:
For information about the pricing rules, see Configuration change fees.
Scenarios
After you enable the automatic performance scaling feature for a database instance, DAS automatically scales up the database instance during peak hours. This can double the read/write throughput and lower the CPU utilization from higher than 90% to 25%. The database instance can run under a heavy load for approximately 10 hours. After the traffic decreases and the CPU utilization drops to lower than 25%, DAS sends messages to suggest you to scale down the database instance to the original specifications.
This way, DAS can manage your database instance to handle traffic spikes during peak hours and help ensure the stability of your business.
Impacts
- When your database instance is being scaled up or scaled down, a transient connection that lasts approximately 30 seconds may occur. Make sure that your application is configured to automatically reconnect to the database instance.
- If the database engine of the database instance is not of the latest version, DAS updates the database instance to run the database engine of the latest version when DAS scales up the database instance. This ensures the performance and stability of your database instance.