RT-CLOSE, a confirmed service, maps directly to A-RELEASE to provide orderly release from an association. The side of the association that wishes to use RT-CLOSE must be the one whose turn it is to transmit data. Since only the one entitled to send data is allowed to initiate the process of closing the association, there will be no chance of data sent by the other side crossing the close request in transit. RT-CLOSE cannot be invoked while an RT-TRANSFER is in an incomplete phase (RT-TRANSFER.request has been issued, but RT-TRANSFER.confirm has not arrived.) RT-U-ABORT maps directly to the A-ABORT service of ACSE to provide a prompt termination with the possibility of lost data. RT-P-ABORT is issued by the RTSE service provider to notify its user of a failure from which recovery is not possible. It will most often happen as a result of RTSE receiving an A-P-ABORT from ACSE.