Use the No Connection alert in Mini DBA to monitor Oracle instances and make this condition visible before it becomes a wider database incident.
Mini DBA describes this alert as: The Oracle server cannot be contacted, either Mini DBA does not have permission to connect or the instance is down The default evaluation frequency is Minute, so the alert is intended to be close enough to operational reality for live triage. Because duration is used, Mini DBA can avoid treating a single short spike as a full incident when the condition clears quickly.
This alert protects availability by warning when Mini DBA cannot reach the monitored Oracle instance or when the service state changes unexpectedly. It is often the first signal that users will see connection failures before deeper diagnostic metrics can be collected.
Enable it on every production and customer-facing Oracle instance. For development systems, keep it enabled only when the instance is expected to be continuously available or when it supports automated testing and demos.
Duration is used, so prefer requiring the condition to persist before paging people for transient spikes. This alert is not primarily driven by a numeric threshold in Mini DBA. Tune the schedule, scope, severity, and notification route so that the alert matches the importance of the instance. Use higher thresholds on batch-heavy, development, or intentionally bursty systems where brief pressure is expected. Use lower thresholds on latency-sensitive production systems, small instances with little headroom, and services with strict recovery or availability commitments.
Confirm the host, listener, service, firewall, DNS, and credentials first. Check whether planned maintenance is in progress, then use the relevant Oracle activity and service logs to decide whether the problem is network, engine startup, authentication, or resource exhaustion.
If this alert is noisy, check whether the workload naturally has short bursts. Raise the duration or threshold for expected batch windows, but keep a lower route for production systems where user-facing latency matters. Avoid simply disabling the alert until you know whether the noise is caused by threshold choice or by a real capacity trend.