Short answer is needed not a long paper.Elaborate on two maintenance strategies

Short answer is needed not a long paper.Elaborate on two maintenance strategies that you would apply to lessen the effect of an already tightly coupled software that you have to maintain for an organization that requires 100% uptime on its safety-critical system. Provide a justification as to why you would implement these strategies over other options that are available. Describe how your strategies would change if the system only required 90% uptime and could be shut down for short periods of time during nonbusiness hours.