The typical definition is where standard data management approaches do not work due to high volume, velocity, and/or variety of data sources. What are standard

The typical definition is where standard data management approaches do not work due to high volume, velocity, and/or variety of data sources. What are standard data management approaches? I don't know. Usually they mean single machine relational db's. But the thing is that once you get to a certain point on these three you need specialized solutions. High volumes of transactional data with real-time reporting might be handled well by something like Postgres-XC, but that won't handle data of sufficient variety. High velocity data may be best handled with something like VoltDB, but it can't handle volume. Etc....