Uptime, quite literally, is the opposite of downtime. It is a measure of the time duration for which a computer can work at a stretch and remains available. Downtime, as is obvious, means the time for which it remains non operational due to functional issues or otherwise. It is used for measuring the stability and reliability of a computer operating system.
More specifically put, it is a measure of the time for which a computer can be left unattended without requiring a reboot for maintenance and administrative purposes or can be left to itself without crashing. However, very long uptimes can indicate some degree of negligence because some updates that are critical in nature can require rebooting on certain platforms.
Today, this measure has a critical success pointer for IT systems. Apart from keeping track of other performance monitors, how long the computer can remain operational without a breakdown is also monitored sustainably for determining system performance. It is always measures in percentage. So, an Uptime of 90% in a day would mean that system can remain active and alert without crashing or requiring reboot for about 21.6 hours which is 90% of 24.
With time becoming increasingly precious in today’s business scenario, the tolerance for unprecedented downtime is dwindling fast. And this is what makes this measure so very relevant.