Oracle Fatal Background Processes

When talking about Oracle background processes, there’s a term/qualifier “fatal” background process. This means that when one of these background processes crashes, then whoever detects the process disappearance (PMON or LGWR or CLMN possibly), will shut down the instance as it cannot function normally anymore.
Not all background process crashes take down the whole instance, for example processes like J000 and P000 are technically background processes (daemons disconnected from network), but their crash won’t take down the instance.