if i understand you correctly you want to relate to tables in 2 different databases, so i think the first step is to create a database link.
the other thing is that since you are you using ArcGIS for your layers, why don't you use sde spatial views for merging to feature classes.
when i try to install cx_Oracle-5.1-11g.win-amd64-py3.1 i am getting the following error message :
this installation package is not supported by this processor..
i don't now how to overpass this error, can you help me to overpass it ??
thank you again.
softwares: WindowsXp professional service pack 2, Oracle Enterprise Manager Version 22.214.171.124.0,