mission-critical 
adjective Computing
(Of hardware or software) vital to the functioning of an organization.This is an important consideration if you are thinking about buying mission-critical software from outside your country....
- Long after the marketing campaign is done, we will still be fanatical about providing the most secure mission-critical software in the business.
- Less than half of the companies surveyed have formal procedures in place for backing up mission-critical data hosted on laptop computers.