Introduction
Delayed market data can only be used with [EClient.reqMktData](/tws-api/doc/market-data-live/top-of-book-l-1/request-watchlist-data) and [EClient.reqHistoricalData](/tws-api/doc/market-data-historical/historical-bars/requesting-historical-bars). This does not function for tick data.
The API can request Live, Frozen, Delayed and Delayed Frozen market data from Trader Workstation by switching market data type via the EClient.reqMarketDataType before making a market data request. A successful switch to a different (non-live) market data type for a particular market data request will be indicated by a callback to EWrapper.marketDataType with the ticker ID of the market data request which is returning a different type of data.
- A EClient.reqMarketDataType callback of 1 will occur automatically after invoking reqMktData if the user has live data permissions for the instrument.

