Use read-only replicas

You can create up to seven read-only replicas for a primary/secondary instance. Read-only replicas are ideal for storing hot data in scenarios with lots of concurrent reads but infrequent writes.

Limits

• A read-only replica cannot exist by itself. It must be associated with a primary/secondary instance.
• A read-only replica is a single node that only accepts reads. Multiple read-only replicas share the same VIP.
• You do not need to set parameters or configure security groups for read-only replicas. A read-only replica inherits all parameter settings and security group configuration from the primary/secondary instance with which the read-only replica is associated.
• The memory capacity of a read-only replica is the same as that of the primary/secondary instance with which the read-only replica is associated. You can add and delete read-only replicas. When you change the memory capacity of a primary/secondary instance, the change also applies to the read-only replicas of the primary/secondary instance. You cannot change the memory capacity of a read-only replica separately.
  For more information, see Change instance configuration.

Manage read-only replicas

You can create read-only replicas for a primary/secondary instance and increase the number of read-only replicas of a primary/secondary instance. You can view and manage read-only replicas in the read-only instance list.
On the Instances page, find the instance for which you want to manage read-only replicas and click Manage in the Actions column. On the instance details page that appears, click Read-Only Instance in the left navigation pane to go to the read-only instance list.

Create read-only replicas

You can specify the number of read-only replicas when you create a primary/secondary instance. The specifications of the read-only replicas are the same as those of the primary/secondary instance.
If you have not specified the number of read-only replicas when you create a primary/secondary instance, you can later add read-only replicas in the read-only replica list.

Add read-only replicas

• On the Instances page, find the instance for which you want to manage read-only replicas and click Manage in the Actions column. The instance details page appears.
• On the instance details page, click Read-Only Instance in the left navigation pane to go to the read-only instance list.