In my middleware course, we discussed the true meaning of oneway in CORBA IDL. The standard and most other sources agree that oneway has at-least-once defines that oneway has at-most-once delivery behaviour, meaning that such operation calls might not be processed by the server, but if they are, then only once. But some students (and many sources) then automatically equate oneway with asynchronous procedure calls, which is wrong (check CORBA AMI). There is still no returning of a result value. The client calls and continuous immediately.

It also turned out that the detailed oneway semantic is not as ORB-dependent as you might think. Since GIOP 1.2, there is the SyncScopePolicy that allows to specify ‘how reliable’ the client ORB should deliver the message. Beside the standard (non-regulated) behavior, you can demand at least acceptance by the servant-side TCP stack (SYNC_WITH_TRANSPORT), reception by some servant (SYNC_WITH_SERVER), or even the processing as with a normal synchronous method (SYNC_WITH_TARGET).