EP, we run 6 production databases (9i and 10g) on one cluster and 60 devl type databases on another cluster. We run multiple dbs on each OH (9204/9206/9208/10203). Each cluster has its own private interconnect (no surprise there) and we don't see many issues. As long as your servers are sized appropriately to handle the load, I don't believe you should run into lot if problems. I don't however recommend putting too many production databases on one cluster though. As for UDP, there are some matrices that you can measure and udp_send/receive size can be set appropriately to make it more efficient. rjamya