Hi all, hope you can help.
Basically, I need my tomcat to startup even when the Entity beans in the application don't correctly correspond to the database schema.
Is this at all possible, and if so how?

I understand this is probably an unusual requirement but let me explain:

I have a service that is rather busy (on average 50 000 000 requests per day), it runs on Amazon AWS and have multiple redundant servers with load balancing between them. The problem is when we do an upgrade that requires changes to the database, I need to first make the change on the database side before I can upgrade the web application/s. This is a problem as all other tomcats (redundant duplicates) will fail to persist data until upgraded, so I'm forced to shut all tomcats down before doing the db changes - This results in downtime.

What I would like to do is:
Upgrade all the tomcats first then upgrade the database (No downtime),
The application has been written in such a way that the database doesn't need to be available or have the correct schema, all events that trigger a insert/update are put into a queue (in memory) and will be persisted when the schema is correct, but lost on shutdown.

I am using:
Java6
Spring 3.0.5.RELEASE
Hibernate-core 3.6.0.Final
Hibernate-entitymanager 3.6.0.Final
Hibernate-validator 4.1.0.Final
Mysql-connector-java 5.1.13
Mysql 5.5