One Cancels the Other Order (OCO)
A pair of conditional orders known as one-cancels-the-other (OCO) instructions specify that if one order executes, the other will be immediately canceled. On an automated trading platform, an OCO order sometimes combines a stop order and a limit order. The other order is automatically canceled when the stop or limit price is reached and the order is executed. OCO orders are used by seasoned traders to reduce risk and enter the market.
Order-sends-order (OSO) circumstances, in contrast to OCO orders, cause the execution of a second order rather than its cancellation.