Enabling optimistic locking on NetWeaver

Hi,

I want to use optimistic locking on selected EJB entities. I annotated an entity-Attribute as @Version (type long) and changed isolation level on the data source alias to 'transaction read committed'. But the entities version-attribute is not incremented and no exception is thrown. What do I need to do in order to make optimistic locking work in NetWeaver 7.31 / JPA 1.0 and MaxDB?

Thanks.

Regards

Anja