During first-time installation the RKM installs some ODI objects into the SAP system. This installation consists of two parts: some base objects and some RFCs. When the RKM options UPLOAD_ABAP_BASE and UPLOAD_ABAP_CODE are both set to true, the base objects and the RFCs are installed. Such full installation requires that no ODI SAP objects are installed in the SAP system. See Uninstalling ODI SAP Components if needed.
If the ODI objects installed into your SAP systems have been installed by RKM SAP ERP v34 or later / RKM SAP BW v25 or later, there is no need for reinstalling the base objects and it is sufficient to update just the RFCs. Reinstalling the RFCs is achieved by executing a reverse engineering run with RKM option UPLOAD_ABAP_BASE set to false and RKM option UPLOAD_ABAP_CODE set to true.