The time/space vortex would close in on everyone and life on the planet as we know will cease to exist.
You can have nested transactions, in some cases with
EJB, you can define the EJB method to Require, RequireNew, Mandatory, None, etc, for different situations having to do with a Transaction already in place and if the method call joins that transaction or creates a new one, or suspends the first one.
Mark