In MSDN, there's a good explanation how to connect BizTalk and SAP with the WCF-Custom-Adapter. However, if you want to send big IDocs, there are some boundaries:
If you use the action Idoc, you could get an exception like: "Failed to allocate a managed memory buffer of 123982965 bytes. The amount of available memory may be low."
If you use SendIdoc instead, you get an exception in the receive pipeline: "Attempt to pass a delimited field greater than the maximum field length of 50000000."
As soon as I find something out, I post it here.
