In my scenario messages on CRM are created by a BADI calling an ABAP proxy class on the local Integraton Engine which then forwards the messages to the XI Integration Server and vice versa.
We recently had the problem that the SAPSLDAPI SM59 destinations on XI and CRM ran into a timeout because the SAPSLDAPI service in the JCo RFC Provider Service of the J2EE Admin Tool was not working properly.
While we experienced the SAPSLDAPI timeout problem in the XI Integration Server all messages which XI was supposed to forward to CRM failed in the Call Adapter step in SXMB_MONI with error status 500 (timeout).
I would have assumed that the same happens also on the CRM side when the local Integration Engine was supposed to send messages to XI. However, there was a timeout when pressing the save button in the IC Web Client. The XML messages were not created at all and not visible in SXMB_MONI. Thus in production a call center agent would have not been able to update any customer or product information.
If such a problem arises in my opinion the messages should always be created and queued up by the Integration Engine so that they can be reprocessed once the problem is solved. Does anybody have any idea why this did not happen on the CRM side and do you have any feedback how this problem could be resolved?