<p>Temporarily sets the state of an alarm for testing purposes. When the updated state differs from the previous value, the action configured for the appropriate state is invoked. For example, if your alarm is configured to send an Amazon SNS message when an alarm is triggered, temporarily changing the alarm state to <code>ALARM</code> sends an SNS message.</p> <p>Metric alarms returns to their actual state quickly, often within seconds. Because the metric alarm state change happens quickly, it is typically only visible in the alarm's <b>History</b> tab in the Amazon CloudWatch console or through <a href="https://docs.aws.amazon.com/AmazonCloudWatch/latest/APIReference/API_DescribeAlarmHistory.html">DescribeAlarmHistory</a>.</p> <p>If you use <code>SetAlarmState</code> on a composite alarm, the composite alarm is not guaranteed to return to its actual state. It returns to its actual state only once any of its children alarms change state. It is also reevaluated if you update its configuration.</p> <p>If an alarm triggers EC2 Auto Scaling policies or application Auto Scaling policies, you must include information in the <code>StateReasonData</code> parameter to enable the policy to take the correct action.</p>

{
  "success": true,
  "data": {
    "id": "abc123",
    "created_at": "2025-01-01T00:00:00Z"
  }
}

{
  "success": false,
  "error": {
    "code": "VALIDATION_ERROR",
    "message": "Invalid request parameters"
  }
}