When I tried migrating my JBoss 4.2 application which uses Spring to manage transactions, to JBoss 5.1, I got the following error message.
Specification violation [EJB3 JPA 6.2.1.2] – You have not defined a jta-data-source for a JTA enabled persistence context
This is a known issue and there are two known workarounds for this problem. See article for details.
