Party Merge Error-how to setup allow parties to participate in multiple hierarchies

 Dear experts,

Party merge is erroring with the error"The following parties cannot be merged because they belong to separate hierarchies. Please remove the hierarchy relationship for one or more of the parties or have your administrator allow parties to participate in multiple hierarchies"

Can any one suggest how to setup foe allowing Parties to participate in multiple hierarchies.

Hope this applies to Oracle Trading community Architecture also.

Thanks

satya