Moving from Full HRMS installation to Shared

Hello,

   I am looking for requirements and heads ups as we transition from using Oracle HR and Payroll to another third party system. Our Oracle EBS system will continue to use financial modules, purchasing, inventory, enterprise asset management, and other supporting modules. However, we still need core basic data to flow from the new third party system to Oracle in support of the remaining applications. In this case, do we need to move the HRMS from full installation to shared? if not, what data do we need to maintain in Oracle EBS? What consequences if any in maintaining full HRMS