How to remover a database system from oem without removing the underlying database instance from oem

AFter adding a few rac databases to our oem  , we noted that the second instance  of each rack had gotten its own database system.

example 

rac is called d

the nodes are  d and d2

in Our oem there now exists a d_sys  and a d2_sys. This seems to have arisen due to the fact that the second node was fist added as a stand alone database  and then  forced into the rac condifuration.

so both  d and d refer to database instance  2.

when I try to remove the unwanted sys s I get a warning that the underlying instance will also be removed. and this is indeed the case. the same happens when you do this via the cli command.