On BigONE, ImmediateOrCancel (IOC) is an effective execution method of the Advanced Limit Order. An immediate or cancel order (IOC) is an order to buy or sell a token that executes all or part immediately and cancels any unfilled portion of the order.
For example, you want to buy 400 BTC immediately, the orderbook at the time looks like this:
If you do not want to pay a price higher than 6655.0 USDT/BTC to buy BTC, then you can you use ImmediateOrCancel (IOC) to execute the limit buy order, which has a limit price of 6655.0 USDT/BTC.
Since there are only 200 + 100 + 3 = 303 BTC sell orders that can be filled immediately at the order limit price or better, the filled sell order is executed. You receive 303 BTC immediately, and the remaining 400 - 303 = 97 BTC unfilled buy order is canceled.