From
EJB spec Pg 352
Containers may optionally support the use of the NotSupported, Supports, and Never
transaction attributes for the methods of entity beans with container-managed persistence
because the use of these transaction modes may be needed to make use of container-managed
persistence with non-transactional data stores. In general, however, the Application Assembler
should avoid use of the NotSupported, Supports, and Never transaction attributes for
the methods of entity beans with container-managed persistence because it may lead to inconsistent
results or to the inconsistent and/or to the partial updating of persistent state and relationships
in the event of concurrent use.
I hope this is clear now..
Amit