To quote the Hibernate documentation:
For use inside an application server, you should almost always configure Hibernate to obtain connections from an application server
javax.sql.Datasourceregistered in JNDI.
What you're trying to do here smells a bit. It kind of defeats one of the main purposes of using a connection pool.
Are you by any chance trying to force your database transactions to commit?
Maybe we can find a better way to achieve what you're trying to do.