tnsnames.ora
When the Deployment Server installer installs the local Oracle database (E1Local),
            the \bin directory is added to the start of the Windows PATH. If you
            have both the local Oracle database and the Oracle client installed (for example, if you
            are connecting to an Oracle database on a machine other than the Deployment Server), the
            local Oracle database version of the executables and tnsnames.ora are
            used. In order to maintain functionality of the Oracle client, you should add the remote
            database server tnsnames entries into the tnsnames.ora used by
                E1Local, which is located in this directory:
<OEE_installation_path>\network\admin
By default, the <OEE_installation_path> is
                C:\Oracle\E1Local, but the actual value is specified during OEE
            installation.