SAP-PI - RFC call to SAP backend system
my scenario is as follows:
I want to implement a RFC-call in SAP-PI to my backend SAP-system
(Receiver system for the IDoc) in order to insert a new entry in a z-table
in the backend system. This will be done by implementing an RFC-enabled
function module in the backend system. If the RFC-enabled FM returns an
exception I want to temporarily set the IDoc in PI "on hold".
After some time (for ex.30 min) I want to try to perform the RFC-call again.
If the RFC-enabled FM in the backend system this time does not return any
exception, then the processing of the IDoc should continue in PI, i.e the IDoc
should be transferred to the receiver system.
In the SAP-PI documentation in URL http://help.sap.com/saphelp_nw04/helpdata/en/cf/406642ea59c753e10000000a1550b0/frameset.htm
it is written:
When a mapping program is executed on the Integration Server, the lookup API
calls the required application system by using the central Adapter Engine.
The call is synchronous. This means that the adapter called returns the result of
the call immediately (not represented in the graphic).
My questions to this forum are as follows
1) Does "synchronous call" in the context above concrete mean that the adapter is
waiting for the completion of the RFC function call to the SAP application system,
before it gives the control back to the mapping program via the lookup API?
2) If so, is it possible to implement an error handling in the mapping program (or the
lookup API) if the RFC call returns a negative result?
3) If so, can this error handling in the mapping program (or the lookup API) - in case
of negative result from the RFC function call - temporarily put the inbound IDoc from
the sender (i.e from the external world) "on hold" in order to be re-processed again
4) If so, is it possible to "trigger" the re-processing of the IDoc in PI by a signal from
the backend SAP application system?
If so, how do I give this signal to PI from the backend SAP system in the best way?
Could it be done with a RFC function call from the SAP application system back to PI;
i.e is it also possible to retrieve RFC-calls in PI, not only send RFC-calls?
Or would it be better to "schedule" a program in PI which tries to repeat the RFC function
call for IDocs "on-hold" due to failure in previous RFC call? If so, how do I schedule
such a program in PI?