What is uptime in Value Stream Mapping? How to calculate the same? Please any one can describe.

What is the difference between Run chart and X chart.

Uptime is when processes are actually running. Downtime is the opposite, when a system or process is not operating. Value stream mapping is looking at a process, determining what things can be done to reduce costs and improve output. Quite common in the chemical processing industries where I worked. If something was made with 5 labor intensive steps, what could be done to make the process faster and cheaper and yet maintain quality. The auto industry and the use of robots to weld and paint cars is a prime example.
https://en.wikipedia.org/wiki/Value_stream_mapping

Greetings of the day and Thank you sir...