For optimistic transactions, we don't hold database locks until the commit phase processing of the Java Blend transaction, when we verify that the database values Java Blend has been operating on are consistent with the database state. Transient attributes are not transactional. Java Blend uses JDBC drivers implementing the JDBC specification. No drivers are available that support 2.0 yet. The white paper talks about a single data model for database information and normal transient program data.
Mapped classes can have transient attributes.
However, these attributes are not mapped to the database. Currently the cache is a per-transaction cache and is not shared. Yes, the mapping information is persistent. None of the above, actually. Classes whose objects you wish to make persistent need to be mapped to the database first.