Operational availability is a ratio you can use when you have a computer network or system running. The operational availability is a way to measure how frequent your computer systems are available to access. In an ideal world, you want your operational availability to equal zero. However, if it is higher than zero, it is not the end of the world. But you should try to keep your system up and running for everyone to use.
Determine the period of time you want to calculate your operational availability for. This can be any amount of time, such as a week or a month or a year. For example, assume you want to know your operational availability for a week, which is 168 hours.
Add together any periods of downtime for your system. This includes planned downtime, unexpected downtime or any other time at all that the system is down. In the example, assume you had an hour of planned downtime and four hours of unplanned downtime when your system crashed, for a total of five hours of downtime.
Divide your downtime by your total hours in your period to calculate operational availability. In the example, 5 divided by 168 equals an operational availability of 0.029 or 2.9 percent.