marketDataType()

TWS sends a marketDataType(type) callback to the API, where type is set to Frozen or RealTime, to announce that market data has been switched between frozen and real-time. This notification occurs only when market data switches between real-time and frozen. The marketDataType( ) callback accepts a reqId parameter and is sent per every subscription because different contracts can generally trade on a different schedule.

void marketDataType(int reqId, int type)