Sync - async w/o BPM

Question

I have a scenario where a Bapi functionality(server proxy) is exposed as a webservice .
So scenario will be SOAP -> XI -> Proxy (calls a BAPI).
I was thinking of:
Receiving the call from WS consumer Synchronously and send him back the ACK (just transport level) and end the sync call. Then fwd this request to R3 using Async proxy...but w/o BPM.
Or can we have a Async call from WS consumer to Xi and from there to R3 proxy and some work around to send back transport level acknowledgement to WS consumer from XI  async.
plz suggest...
XI Queries.

Answer 1

Hi,
I think you can handle in the sender client end. Check this note
Note 856597 - FAQ: XI 3.0 / PI 7.0 / PI 7.1 SOAP Adapter
It states :
Sender Asynchronous Calls
Q: What are the correct sender options for asynchronous calls?*
A: The setting in the channel configuration determines how the message is passed to the XI infrastructure. Setting the channel's quality of service to ExactlyOnce guarantees the delivery of the message exactly once between the adapter and the back end. This will not automatically guarantee the delivery with exactly once between the client and the back end. The behavior of the client determines the level of quality of service achieved.
When the client sends a SOAP message and ignores the response completely as in "fire-and-forget", the quality of service with AtMostOnce may be realized.
When the client sends a SOAP message and checks if the response is an HTTP 200 response message with an empty soap envelope or an HTTP 202 response message with no content, the quality of service with AtLeastOnce can be realized. In this case, the client must resend the message until such a successful response is returned. When the message successfully accepted by the adapter, an HTTP 200 response with an empty SOAP envelope or an HTTP 202 response message with no content is returned.
When the client resends the message, there is a possibility that the message may arrive more than once. However, this possible duplicate only happens, when the client previously received no response message at all.For all other cases, the client can resend the message without resulting any duplicate. In order to eliminate duplicates for all cases, the client may send the message with a unique message ID. This message ID will be used to create an XI message so that the identity of the created XI message and that of the original SOAP message are coupled.The client must resend the message with the same message ID, until, a HTTP 200 response with an empty soap envelope/HTTP 202 without content is received as an acknowledgement and client would not get the DuplicateMessageException in this regard.In either case, the client can assume that the message is delivered exactly once (theoretically the message ID could be identical to another message ID used previously but the probability of this is extremely low).
Regards
Suraj