Definition:
Graceful Degradation refers to a system’s ability to continue partial operation when some components fail, avoiding complete shutdown. The system does not simply fail safe by shutting down, but instead maintains as much functionality is possible while still ensuring safety. This is a concept that is baked into the Functional Safety Lifecycle and IEC 61511-1.
More of a concept and not formerly defined by any of the IEC codes.
Key Points:
- Increases availability without compromising safety.
- May involve reverting to manual operation modes.
- 2oo3 architecture is an example of the graceful degradation concept.
Example:
Loss of one out of three redundant sensors still allowing safe operation under 2oo3 voting.
See also: architecture
Cited Source:
- IEC 61508-1:2010.