HACMP works very well but the support that OE has for it is marginal at best.. A cluster solution is not really a cluster solution without multiple mirrored databases live at the same time.
OE Repl plus isn't quite ready for prime time imo... there are a number of issues with quick failovers and the ability to keep the source database up when the target goes down as well as the need to bounce the target database to allow users write access (and to restart it as a source database).
Some of the issues are resolved in 11.6... but most of the issues haven't been addressed. Hopefully in future releases.
It is however better than nothing and marginally better than roll your own AI replication because of the streaming nature of replication. Mostly because you are able to keep your warm database much closer to real time.
Async is the only real option because synchronous replication is just way too slow for any realistic data volumes. Testing simple transactions in synchronous mode added almost a second to a simple create of a basically empty record.
TDE - will add basically no extra steps or overhead to the process other than making sure the dbname.ks files are populated where they need to be.
