Error when opening a saved Data Comparison (.DCP) file: "ORA-12154" or "Can not obtain Oracle..." (4302378)

Error when opening a saved Data Comparison (.DCP) file:

"Can not obtain Oracle client information from registry. Make sure that Oracle Client Software is installed, or use Direct mode of connecting to server."

AND / OR

"ORA-12154: TNS: could not resolve the connect identifier specified"

Add the Windows Environment Variable "TNS_ADMIN" and point it to the location of the tnsnames.ora file.  Also ensure the Oracle Client Home Bin path (for the client you want to use) is in the beginning of the PATH environment variable.