In designing a reliable system, it is recognized that there will be failures. At the extreme, a complete system can be duplicated and kept up to date—so in the event of the primary system failing, the secondary system can be switched in with little or no interruption. More often, a hot spare is a single vital component without which the entire system would fail. The spare component is integrated into the system in such a way that in the event of a problem, the system can be altered to use the spare component. This may be done automatically or manually, but in either case it is normal to have some means of error detection. A hot spare does not necessarily give 100% availability or protect against temporary loss of the system during the switching process; it is designed to significantly reduce the time that the system is unavailable.