If you are removing a database domain that is not hosting a quorum disk, then no action is required.
If you are removing a database domain that is hosting a quorum disk containing a voting file, and there are five or more storage servers in the RAC cluster, then no action is required. When you remove the database node hosting the voting file, the dropped voting file will be automatically relocated to a storage server that did not contain a voting file as part of the voting file refresh.
If you are removing a database domain that is hosting a quorum disk containing a voting file and there are fewer than five storage servers in the RAC cluster, then you must create a quorum disk on a different database domain before you can remove the database node.