The use of setenv for ORACLE_HOME and ORACLE_SID in a downstream configuration

We are configuring Goldengate in Downstream Real Time mode and was wondering if we still need the setenv for ORACLE_HOME?  Is it used to find configuration details for tnsnames, ldap, and sqlnet.ora for connection from the process group to the database with this configuration?  The only thing I could find in the documentation was that it was a required entry, but trying to figure out why it is needed if the processes are not on the same server as the database.  If you have a link to a spot in the documentation where it says otherwise it would be greatly