ApsaraDB for RDS offers four editions: Basic Edition, High-availability Edition, Cluster Edition, and Enterprise Edition. This topic describes the High-availability Edition.

The High-availability Edition is a widely used edition that allows for one primary instance and one secondary instance. These instances work in the high-availability architecture. This edition is suitable for more than 80% of the actual business scenarios, such as the Internet, Internet of Things (IoT), online retail, logistics, and gaming.



High availability

In the High-availability Edition, data is synchronously replicated from the primary instance to the secondary instance. If the primary instance breaks down unexpectedly, your database system automatically fails over to the secondary instance.

You can deploy the primary and secondary instances in the same zone or in different zones.

Note If the secondary instance breaks down unexpectedly, the primary instance must back up data on itself in real time. When such a backup is about to complete, a global lock is triggered by the FLUSH TABLE WITH READ LOCK (FTWRL) statement. The global lock is held for up to 5 seconds. You can only read data from the primary instance when the global lock is held.

Comprehensive functionality

The High-availability Edition supports all of the features that are provided by ApsaraDB for RDS. These features include automatic scaling, backup and restoration, performance optimization, read/write splitting, and SQL explorer. The SQL explorer feature allows you to query logs about the SQL statements executed. This makes database access traceable and ensures the security of important data.


You must deploy the primary and secondary instances in the same region for stable performance.

Upgrade to High-availability Edition

In the Basic Edition, the primary instance does not have a secondary instance as its hot backup. If the primary instance breaks down unexpectedly, is executing specification changes, or is updating its version, it may remain unavailable for a long period of time. If you have strict requirements for service availability, we recommend that you select the High-availability Edition.

In addition to creating an RDS instance designed to run the High-availability Edition, you can upgrade the edition of a created RDS instance from Basic to High-availability. After the upgrade, the new RDS instance inherits the lifecycle of the original RDS instance. Therefore, you do not need to migrate data or reclaim the original RDS instance.


  • Can I access a secondary instance?

    No, you cannot access a secondary instance. You can only access a primary instance. A secondary instance serves only as a backup and does not allow external access.

  • Can I downgrade the edition of my RDS instance from High-availability to Basic?

    No, you cannot downgrade the edition of your RDS instance from High-availability to Basic. You can create an RDS instance that runs the Basic Edition, migrate the data of your RDS instance to the new RDS instance, and then release your RDS instance. For more information, see Migrate data between RDS instances.