An apparatus and method for monitoring a computer system operable for alerting an operator to failures associated with critical resource consumption and comprises: a resource monitoring component for monitoring resource consumption; a threshold setting component for setting a threshold of resource consumption between an average resource consumption value and a critical resource consumption value; a diagnostic data collection component; and a threshold crossing detection component; wherein the diagnostic data collection component is operable, in response to the threshold crossing detection component detecting a threshold crossing, to start or stop diagnostic data collection.