Simple solution for clustering databases via JDBC:

There is also a free trial version available:
http://www.activ8.at/homepage/en/a8cjdbc.php

Some features:
* a JDBC driver so the application does not know anything about the
replication
* of course: transactional safety for write operations
* load-balanced reads (we are running 2 database servers, so why waste
the ability to do parallel reads from 2 servers and almost multiply
the performance by 2?)
* for backups: the ability to detach one server, do the backup on that
machine and then reattach the server
* automatic and transparent failover / failsafe

regards,
Wolfgang