Abnormal Replication Between Primary and Standby RDS DB Instances

Scenario

The replication relationship between primary and standby RDS DB instances is abnormal. A possible cause is that the default security group rule is deleted.

Solution

1. Log in to the management console.
2. On the Instances page, click the target DB instance.
3. On the Basic Information page, click the security group name.
4. On the Inbound Rules tab, click Add Rule. In the displayed dialog box, select All for Protocol & Port and Security group for Source. In the drop-down list, select the same security group as the displayed one on the Basic Information page.
5. Wait until the rule is added. Check that the replication relationship between primary and standby DB instances is restored.