How to achieve failover when the master definition site is down ?

I have two Oracle 8i instances in a multi-master async replication environment. Two J2EE application servers connect to each of the Oracle instance respectively. When one of the oracle instance is down, I'd like to have my J2EE application failover to the second Oracle instance automatically without human intervention. I understand I can use OCI driver to allow my J2EE app to connect to the other Oracle instance when the first is down. But here are some questions:
1. If I understand it correctly, there's only one master definition site. Let's say my master definition site sits with the first Oracle instance. If this server is down, the DBA has to go in to config the second Oracle instance to be the master definition site. Can this be done automatically without the DBA ?
2. If the master definition site is down and the DBA is yet to come in, will the second Oracle instance still work ? I do understand the replication won't work, but will normal database read/write work ? What happens between the master definition site down and the master definition site reconfigured ?
3. Are there any low cost third party tools can handle what I wanted ?
Thanks in advance,

To answer your questions.
1. Yes there is only one master def site, it is not important to relocate the master def site, in the event of its failure. The def site is used as a the source for replication definition generation.
2. It depends upon what type of multi-master replication you have implemented. If you are using asynch replication, the site that is up will continue to allow updates and will queue the transactions. When the other site(s) are active again, it will forward the transactions. Note, this can cause untold problems if you have a heavy used system, and narrow bandwidth. If on the other hand you are using synchanous replication, when one site goes down, the other site(s) lock their tables to prevent dml/ddl changes. Then you have to decide whether or not you can wait for the down site to be restored, or break replication to continue operations.
3. Yes, there are a few, one that comes to mind, I believe is Shareplex.

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