The Order Cancel/Replace Request is used to change the parameters of an existing order.
Do not use this message to cancel the remaining quantity of an outstanding order, use the Order Cancel Request <F> message for this purpose.
It is recommended that the Cancel/Replace Request <G> message be used to partially cancel (reduce) an order.
The request will only be accepted if the order can successfully be pulled back from the exchange floor without executing. Cancel/Replace Requests which cannot be processed will be rejected using the Cancel Reject <9> message; the ClOrdId <11> of the replacement order is inserted in the ClOrdId <11> field of the Cancel Reject <9> message for identification.
Only a limited number of fields can be changed via the Cancel/Replace Request message. All other fields should be retransmitted as sent in the original order. These fields are:
When modifying ExecInst <18> fields in a replacement order, it is necessary to redeclare all ExecInst <18> in the replacement order. ExecInst <18>'s will not be carried forward from the original order to the replacement unless redeclared.