As smallcase is a portfolio of stocks and the whole portfolio has to be purchased in one go, the orders are set to be market orders. As all the stocks which are constituents of smallcase are liquid stocks, the market orders will definitely get traded in NSE. 

Adding IOC (immediate or cancelled) tag to them is just to further ensure that in case a market order doesn’t get traded, it doesn’t become a limit order; it rather gets cancelled if it doesn’t get traded immediately. Thus within few seconds of placing a buy order for the whole smallcase, all the orders are either traded or cancelled and for all cancelled orders, you can immediately place a repair order. (It will be a very rare scenario)