Unplanned outage

Unplanned outage is an unscheduled outage that happens if the system was not set up to handle it by implementing redundancy or failover support, and so on.

Hardware

Unplanned outages can happen due to hardware failures resulting from hardware faults, power failure, natural disaster, and so on.

Software product

Software crashes can lead to unplanned outages as well. Although such a crash should be investigated so that the associated outage can be avoided in the future, most outages can be recovered by just restarting the software application. As such, setting up an automated recovery approach or just restarting the application can be your first line of defense.

Capacity

Even though all the system components may be active and operational it is possible that the system is not operating at the capacity required by your business specifications. For example, the response time has increased past your acceptable time. This could happen due to an increase in workload, but the possibility increases significantly if some of the redundant components fail.
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