There are many snapmanager products - the basic ones are snapmanager for windows/unix. All these do is intall some commands through which you can manage the snapshots on the controller - for example, snap list, snap create, snap delete, etc. The connection is over one of the API channels. The other snapmanager products (for Oracle, Exchange, SharePoint, etc.) utilize the basic snapmanager products for talking to the controllers, but they also talk to the application in question, and will handle all the scheduleing and integration.
Remember that, in a snapmirror relationship, you're copying the source volume and snapshots. What you say about updating a snapmirror relationship creating a snap that is copied to the destination is technically correct, but that process is part of the internal workings, and I find it better just to focus on the volume and non-snapmirror snapshot data. So if you put your DB in hot standby, then issue a snapmirror update, wait for it to finish, then take your DB out of hot standby, you've got a consistent copy of your DB at DR that you could snapmirror back if needed.
If, however, you put your DB in hot standby, take a snapshot, take your DB out of hot standby, and THEN inititate the snapmirror update - which you don't need to wait for to finish - then your destination _volume_ is inconsistent from a DB perspective, because the DB was active when it was copied. The snapshot you took when the DB was in hot standby, though, also gets copied - and that is consistent. Instead of just reversing the direction of the snapmirror, you'd have to break the snapmirror, restore the volume to the desired snapshot on the destination, then mirror it back.
One caveat would be that a snapmirror reversal (as in my first scenario) would only copy incremental changes, while the second scenario would be a full copy - irrelevant in the event of a real disaster,but possibly impactful when faced with corruption. Another benefit of doing just the snapshots would be that you could keep multiple consistent copies around as well.
Make sense?
Bill
