Looks like you have setup Datasources for Oracle and DB2 in your AppServer and using the datasource to obtain a connetion. you will get this exception when you use two different resources (Database, JMS source etc) in a single
EJB Transaction.
One way of getting around is use fixed connection instead of pooled connection, for one of the DBs. And commit/rollback the fixed connection accordingly.
Try making the second method with 'Not supports' transaction attributes, this way the second method will not run in a transaction, but you cannot do commit/rollback on the connection that you use in second method.
(If the exception still occurs, (not likely) make a separate EJB that runs in 'Not supports' transaction mode and call it from method1.