The server I'm using is Websphere 22.214.171.124 with JPA 2 feature-pack version 126.96.36.199, and I configured the server to use parent-last class loader as the IBM JPA documentation stated. The DB server is MS SQL-Server 2008.
Deployment goes fine, and here is the tricky part: On one Websphere I get an exception: QuerySyntaxException: Entity is not mapped
On another Websphere, with exactly the same specs, exactly the same installation process, exaclty same computer model, exactly the same ear file.. all goes well - no exception and persistence is working great.
I compared the drivers (SQLJDBC4), all the paths, the data-sources settings, even tried the same DB - nothing.
I have no clue... There has to be a difference...