I try to change the HSQL DB used by orchestra engine by postgresql DB.
Is it possible using configuration files ?
No, It's not implemented for the moment.
Or may I have to change the Java class :
Yes, you can modify this class.
I think that these configuration parameters must be setted in the
jbi.xml file of the orchestra component. If you have enough time to do
this, does not hesitate to send the corresponding patch.