Impact of closing an alert
In System Center Operations Manager, an alert can be generated by a rule or a monitor. Alerts have two possible resolution states, by default: New and Closed. Administrators can add custom alert resolution states to a management group. For more information, see How to Set Alert Resolution States.
The impact of setting the alert resolution state to Closed depends on whether the alert was generated by a rule or a monitor. Select the alert to display the alert details. The details for an alert will either list Alert Rule or Alert Monitor.
If you close an alert that was generated by a rule and the issue continues or occurs again, another alert will be sent. Closing an alert that was generated by a rule when the issue isn't fixed isn't a problem, because the rule will generate another alert.
However, an alert that's generated by a monitor is sent only when the state for the monitor changes from healthy to some other state (warning or critical). If you close an alert that's generated by a monitor when the issue isn't fixed, no other alerts will be sent.
For example, a monitor for free disk space detects that disk space on a computer is below the configured threshold. The monitor changes the health state to critical (red) and sends a single alert. After the monitor has sent the alert, it won't generate future alerts so long as the health state doesn't change from critical to healthy (green). If you close the alert while the object is in a warning or unhealthy state, the problem remains unresolved but no further alerts will be generated.
However, an alert that is generated by a monitor is sent only when the state for the monitor changes from healthy to some other state (warning or critical). You can't close an alert generated by a monitor as long as the monitor is in Warning or Critical state. Once the monitor is healthy again, Operations Manager either resolves the alert by itself (if auto-resolve is enabled) or you can close the alert manually from Active Alerts dashboard.
For example, a monitor for free disk space detects that disk space on a computer is below the configured threshold. The monitor changes the health state to Critical (Red) and sends a single alert. After the monitor has sent the alert, it won't generate future alerts so long as the health state doesn't change from critical to healthy (Green). You can't close this alert until the actual problem is resolved and the monitor becomes healthy again.
Generally, before you close an alert, you should verify that the issue is resolved. If the alert was generated by a monitor and the alert doesn't resolve automatically, check Health Explorer and the health state of the computer to ensure that the states have returned to healthy before you close the alert.
Next steps
Before changing the number of missed heartbeats allowed, first review How Heartbeats Work in Operations Manager.
To learn more about how to investigate an agent heartbeat failure and ways to resolve them, review Resolving Heartbeat Alerts.
When an alert is generated, you can View Active Alerts and Details in the Operations and Web console to identify possible issues and help identify the next steps towards resolving them.