This topic describes how to create a read-only ApsaraDB RDS for MySQL instance. Read-only RDS instances help increase the read capability of your database system and the throughput of your application. Each read-only RDS instance is a replica of the primary RDS instance. This indicates that each read-only RDS contains the same data as the primary RDS instance. Data updates on the primary RDS instance are automatically synchronized to each read-only RDS instance.
For more information about how to create a read-only RDS instance that runs a different database engine, see the following topics:
- Create a read-only ApsaraDB RDS for SQL Server instance
- Create a read-only ApsaraDB RDS for PostgreSQL instance
For more information about read-only RDS instances, see Overview of read-only ApsaraDB RDS for MySQL instances.
Prerequisites
The primary RDS instance runs one of the following MySQL versions and RDS editions:
- MySQL 8.0 on RDS High-availability Edition or RDS Enterprise Edition
- MySQL 5.7 on RDS High-availability Edition or RDS Enterprise Edition
- MySQL 5.6
Precautions
- You can create read-only RDS instances for the primary RDS instance. You cannot convert existing RDS instances to read-only RDS instances.
- When a read-only RDS instance is being created, ApsaraDB RDS replicates data from the secondary RDS instance to the read-only RDS instance. This prevents interruptions to your workloads on the primary RDS instance.
- After the primary RDS instance is released, the subscription read-only RDS instances of the primary RDS instance are automatically refunded and released, and the pay-as-you-go read-only RDS instances of the primary RDS instance are directly released.
- A read-only RDS instance does not inherit the parameter settings of the primary RDS instance. ApsaraDB RDS generates default parameter settings for each read-only RDS instance. You can modify the parameter settings of a read-only RDS instance in the ApsaraDB RDS console.
- You can create up to 10 read-only RDS instances for a primary RDS instance. If you want to create more than 10 read-only RDS instances, you must submit a ticket.
- Read-only RDS instances support both the pay-as-you-go billing method and the subscription billing method. For more information about the prices of read-only RDS instances, see Read-only ApsaraDB RDS instance types.
- When you create a read-only RDS instance, you must select a virtual private cloud (VPC) that meets the specified requirements. For more information, see FAQ.
Create a read-only RDS instance
View a read-only RDS instance
To view a read-only RDS instance on the Instances page, perform the following steps:
To view a read-only RDS instance on the Basic Information page of the primary RDS instance, perform the following steps:
View the latency of data replication to a read-only RDS instance
A read-only RDS instance may synchronize data from the primary RDS instance at a specific latency. You can go to the Basic Information page of a read-only RDS instance to view the latency of data replication to the instance.

FAQ
- When I create a read-only RDS instance, why am I unable to select a specific zone?
The zone that you select does not have available resources. Select another zone and try again. This does not affect the read-only RDS instance.
- When I create a read-only RDS instance, can I select a VPC that is different from
the VPC of the primary RDS instance?
- If the primary RDS instance resides in the classic network, you can select the classic network or a VPC. The selected VPC can be different from the VPC of the primary RDS instance.
- If the primary RDS instance resides in a VPC:
- You can select the classic network.
- If local SSDs are used, you can select a VPC. The selected VPC can be different from the VPC of the primary RDS instance.
- If standard SSDs or enhanced SSDs (ESSDs) are used, you can select only the VPC of the primary RDS instance.
- When I create a read-only RDS instance, ApsaraDB RDS replicates data from the secondary
RDS instance to the read-only RDS instance. This prevents interruptions to your workloads
that are run on the primary RDS instance. What is a secondary RDS instance?
If you are using the RDS High-availability Edition, your database system consists of a primary RDS instance and a secondary RDS instance. These instances work in the classic high-availability architecture. If the primary RDS instance becomes faulty, your database system fails over to the secondary RDS instance.
Related operations
Operation | Description |
---|---|
Create a read-only instance | Creates a read-only ApsaraDB RDS instance. |