EJB JTA / JPA CMT事务回滚会影响子事务

I'm having a problem with transaction rollback in which a sub-transaction annotated with REQUIRES_NEW is being rolled back because the parent transaction was rolled back. I am puzzled because I had thought that JTA/JPA treated these transactions independently so that rollback on one did not affect the other. I'm using Java 1.6.0_24, EJB 3.1, GlassFish 3.0.1, JPA 2, MS SQL Server (non-XA) 2008, CMT. I'm having a problem with transaction rollback