FIX Protocol tutorials: Difference between Session Level Reject and Business message Reject
In FIX protocol there are multiple ways of rejecting message some of them are using an Execution Report (MsgType=8) and ExecType=8 to reject a FIX message if it can not be acceptable by exchange e.g. Sending order for an exchange and link between broker and exchange is down. Another way of rejecting message is OrderCancelReject (FIX MsgType=9) which is used to reject amend (OrderCancelReplace message FIX MsgType 35=G) and cancel (OrderCancelRequest FIX MsgType=F) messages if its not possible to modify or cancel original message e.g. Sending Cancel request to an already filled order will be rejected by OrderCancelReject message in FIX protocol.
