Oneagent has a watchdog process, that will start up any crashed oneagent subprocesses (e.g. oneagentos, oneagentplugin... ). The deep-instrumented processes will continue to operate and send data even if Oneagent is shut down, since the instrumentation and data collection is not dependent on Oneagent running.
Do you mean to say deep-instrumentation data collection will continue to happen even if OneAgent has gone down but sending of this data to the Dynatrace server will only happen once OneAgent comes back up? How will Dynatrace server receive the data if not through OneAgent, is there another way? Thanks for clarifying.
As Julius mentioned, the watchdog will automatically restart it.
If you wan't to know if it crashed you can check the Event Viewer on Windows or check the service status with systemd on linux.