ISM Environment Variables

I continue my life's work trying to make ISM work in a number of different environments. Recently I have been exploring the ability to restore from onbar/ISM to a different system (The imported restore). During this I have discovered that it is necessary to set environment variables ISM_CLIENT and ISM_SERVER. The documentation only mentions these in connection with imported restore and gives no other idea as to their use. However it does refer to hostname and not server or instance name. I would appreciate pointers to any documentation on ISM_CLIENT and or ISM_SERVER and any guidance that the august members of this list can offer regarding using onbar/ISM in a multiple residenct situation. regards Malcolm