ApsaraDB for Redis uses scheduled events to notify you of upcoming maintenance operations — such as migrations, version updates, and certificate renewals. Each event includes an impact estimate and a recommended action so you can plan accordingly.
For console procedures to view events and modify or cancel their scheduled time, see Scheduled events of database services.
Event types
Steps inside the red boxes in the process flowcharts have a direct impact on the service.
| Type | Process | Impact | Cause | Recommended action |
|---|---|---|---|---|
| Instance migration |  | Transient connections; read-only for 30 seconds | The host machine is experiencing issues | S0: Migrate to the new instance immediately |
| Minor version update |  | Transient connections; read-only for 30 seconds | The current minor version contains risks or security vulnerabilities | S1: Update the minor version. The new version is backward compatible. |
| Proxy minor version update | Proxy nodes are updated in small, incremental batches | Transient connections lasting several seconds | The current proxy node minor version contains risks or security vulnerabilities | S1: Update the proxy node minor version immediately. The new version is backward compatible. |
| SSL certificate renewal | 1. Renew the SSL certificate:  2. Update proxy nodes in small, incremental batches | Transient connections; read-only for 30 seconds | The SSL certificate has expired | S0: Renew the certificate immediately. After expiration, connections to the instance may fail. Do not cancel this event. |
| Major version upgrade |  | Transient connections; read-only for 60 seconds | The current major version is end-of-life | S1: Upgrade the major version immediately. The new version is backward compatible. |
Severity levels
Events are classified into two severity levels that determine notification lead time and your ability to reschedule or cancel.
| Level | Name | Description | Notification lead time | Cancelable |
|---|---|---|---|---|
| S0 | Critical | Unexpected issues requiring immediate action to prevent system failure. Applies to: emergency version replacements, host exception fixing, and SSL certificate renewal upon expiration. | At least 3 days in advance | No — the window to modify the scheduled switchover time is limited |
| S1 | High | Low-risk, scheduled maintenance such as software or hardware upgrades. | More than 3 days in advance | Yes |
FAQ
Can I cancel an S0 event?
S0 events address critical issues — such as SSL certificate expiration or host failures — that can cause service outages if left unresolved. The window to modify the scheduled switchover time is small. Act on S0 events as soon as you receive the notification.
Will a version update break compatibility with my existing application?
No. Both minor version updates and major version upgrades are backward compatible. Your application does not need to change after the update.
What is the actual downtime during a scheduled event?
The impact depends on the event type:
Instance migration, minor version update, SSL certificate renewal: transient connections plus up to 30 seconds in read-only state.
Major version upgrade: transient connections plus up to 60 seconds in read-only state.
Proxy minor version update: transient connections lasting several seconds (shorter, because proxy nodes are updated in small batches).
For additional questions, see FAQ about scheduled events.
API reference
Use the following API operations to query and manage scheduled events programmatically.
| API operation | Description |
|---|---|
| DescribeActiveOperationasks | Queries information about multiple proactive O&M events |
| ModifyActiveOperationTasks | Modifies the scheduled switchover time of O&M events for an instance |
| CancelActiveOperationTasks | Cancels the O&M events of an instance |