Which term signifies a period of system unavailability due to failure?

The term that signifies a period of system unavailability due to failure is "Down Time." This term specifically refers to intervals when a system is not operational, which can be caused by various factors, including hardware failures, software bugs, or other unexpected issues. Understanding this term is crucial for businesses and IT departments because down time can lead to service disruptions, affecting customer satisfaction and operational efficiency.

The other terms do not convey the specific meaning of system unavailability due to failure. Draft Processing refers to the preliminary phase of payment processing where transactions are prepared for submission. Network Running indicates that the system or network is functioning and operational. System Maintenance involves scheduled activities to ensure systems are running smoothly but does not imply unavailability due to a failure; instead, it is often planned to minimize disruption. Hence, "Down Time" is the most accurate choice for describing a situation where systems are unavailable due to failure.