I'm planning to move to Hibernate using a J2EE DataSource for connection pooling and JTA transactions.

Could I mix Hibernate and JDBC within the same transaction?
What if I access/update the same table with both Hibernate and JDBC within the same transaction?

Thanks.

GDay Mate - sorry could not help myself. :-)

Yes you can use both during the same transaction, Get the JDBC connection from the session. Database will be updated appropriately by the transaction.
You will loose caching benefits where same issues apply if the data was updated from another source.

How do you mean?
Will I have to turn caching of by some setting?
Or will Hibernate detect that my database is "dirty" and re-read?

Hibernate cannot see what you did to the DB, so object cache will not be updated or dirtied by Hibernate. You have to do it manually by refreshing some object.