Thank you Ankita!
I believe I didnt explain myself properly. I'm aware I have to trigger OB from RCM, however, what I need to decide is when the employee will be created in SAP.
I can create the employee from RCM in SAP (despite the fact that RCM will trigger also OB), or I can create the employee in SAP from OB.
Does my question make sense?
Thank you once again!