RMAN 6217 not connected to auxiliary database with a net service name

Error:    RMAN 6217 (RMAN-06217 RMAN-6217)
Text:    not connected to auxiliary database with a net service name
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Cause: A command that moves files from the target instance to the
       auxiliary instance was requested.  Such a command requires a
       net service name be present in the connect string used to
       connect to the auxiliary instance.

Action: Issue a CONNECT AUXILIARY command and include a net serice name
        in the connect string.  That service name must be valid on
        the target instance.