An RDS instance typically undergoes a primary/secondary switchover to patch vulnerabilities, respond to a manual operation, or recover from an instance failure.
A primary/secondary switchover occurs for one of the following reasons:
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Potential vulnerabilities
Alibaba Cloud may detect a potential vulnerability on your instance that could affect its operation. To resolve this, the system first applies a patch to the secondary instance and then initiates a primary/secondary switchover during your specified maintenance window. For critical vulnerabilities, the system triggers the switchover immediately.
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Manual operations
You or an authorized Alibaba Cloud technical expert can manually initiate a switchover.
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Instance failures
If Alibaba Cloud detects a failure that prevents your instance from operating normally, it initiates a primary/secondary switchover to restore service.
After a primary/secondary switchover is complete, the instance status changes to Running. You do not need to take any action, and the instance will operate normally. You can view the switchover details in the Primary/Secondary Switching Logs section on the Service Availability page for your instance.