Where is the PTCS_GETAUTHORIZATION service operation triggered?

In our PeopleSoft environment we have several domains (CRM, ELM, FSCM, HCM and iHub).  We have some users who are not in all of these domains. For example, the vendors only exist in iHub and FSCM.

Whenever a user signs into iHub the PTCS_GETAUTHORIZATION service operation is published from iHub to CRM, ELM, FSCM and HCM. This service operation will fail in iHub when the service operation is being published to a domain where the user does not exist.

Where is the PTCS_GETAUTHORIZATION service operation published in iHub? We would like to prevent this service operation from being published to a domain the user does not exist.