A TruthValue, read-create, controlling whether each new histogram update is summed cumulatively with prior data or replaces it with only the latest snapshot. This changes how cwrHistSummaryTable should be interpreted, as a running total across the whole collection versus a rolling window of just the most recent update period. For example, setting cwrHistPeriodicSum to true would let an engineer track total occurrences of an error attribute over an entire multi-hour capture rather than only the last cwrUpdateRate interval.