Once a transaction judges a system to be available and accurate, the Overall Health rating of that transaction is calculated based on the Performance rating.
If a system is not working accurately or is unavailable (either Accuracy or Availability equal 0), the Overall Health rating will be 0.
As Overall Health is based on the Performance health dimension value, it is an absolute rate not expressed in percentages (for example, 50, 80, etc.).
Overall Health = Performance