sqlnet2.1 & local instance connections

we are updating from sqlnet 1 to sqlnet 2.1.5.

We have a multinode vms cluster running parallel query.

We want to create some data base links which connect automatically connect to an instance on the current node.

e.g.
select * from sys.dual_at_current_node_db

instead of using one of the node names.
select * from sys.dual_at_machine1_db
select * from sys.dual_at_machine2_db

on sqlnet 1 you could do something like the folowing create public database link current_node_db using '2:512,<file>';

where <file> was the name of an sqlnet program file that worked out what node it was on and from that what the local instance was called and then connected to that instance.

How do I do something similar in SQLNet 2

Thanks,

Duncan

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