The following code prints "null" to the console with the embedded driver:
Statement s = c.createStatement(ResultSet.TYPE_FORWARD_ONLY,
ResultSet rs = s.executeQuery("select * from sysibm.sysdummy1");
c.createStatement().executeQuery("values 1").close(); // causes auto-commit
The call to rs.getString() should perhaps have thrown SQLException, since the auto-commit between next() and getString() should close the ResultSet when the holdability is CLOSE_CURSORS_AT_COMMIT, I think. Anyway, the value stored in SYSIBM.SYSDUMMY1 is 'Y' and not NULL, so it should definitely not return null.