Two connections in one transaction?

[alex seba]

Hi,
I'm using a stateless Session Bean as a facade to some Entity Beans. All transactions are managed by the container.
I want to have access to two connection pools within one transaction. I'm using a DB2 with the COM.ibm.db2.jdbc.app.DB2Driver and an InstantDB with the org.enhydra.instantdb.jdbc.idbDriver. I know that it must be possible as these drivers support XA-Transactions.
But with my setup I'm getting a java.sql.SQLException that there cannot be two connections within one transaction. Can anyone give me some hints how to setup my JTA properties for this scenario?
Thanks in advance
Alex