Recently I was on a site who run a DG for each instance, the server with highest number of instance was 4 though. In total they have around 12 instances so 12 DG. Whenever they have a new instance they create a new Service Guard package which includes a ORACLE_HOME (right now for example they have 12 ORACLE_HOME), a new DG.
For a 1.5TB new Database with static data I suggested to create a new instance, they were cautious because that meant a lot of work!
I know some of you folks have large SMPs as the result of consolidating from a lot of little SMPs into one large one for managability sake. What about distaster recovery? If you have, say, 20 databases in a large SMP, do you set up 20 "streams" of DG to a DR site? Is that a nightmare? Are there any sites out there that have, say, more than 10 databases that require disaster protection where DG is the tool of choice? Or do such sites opt to replicate at the storage (or volume e.g., Veritas VVR) level?
Yes, Carel-Jan will remind us that replicating at the storage level requires replication of all writes as opposed to just sending redo pieces…