Holds strong references to a set of remote objects, or live remote references to remote objects, after they have been marshalled (as remote references) as parts of the arguments or the result of a remote invocation. The purpose is to prevent remote objects or live remote references that might otherwise be determined to be unreachable in this VM from being locally garbage collected before the receiver has had an opportunity to register the unmarshalled remote references for DGC. The references are held strongly until an acknowledgment has been received that the receiver has had an opportunity to process the remote references or until a timeout has expired. For remote references sent as parts of the arguments of a remote invocation, the acknowledgment is the beginning of the response indicating completion of the remote invocation. For remote references sent as parts of the result of a remote invocation, a UID is included as part of the result, and the acknowledgment is a transport-level "DGCAck" message containing that UID.