SAP JCo JCoServerTIDHandler and/or JCoIDocHandler interfaces

Question

we're currently setting up a SAP-IDoc JCo-Server.

There are two interfaces for transaction management und receiving IDOCs.

Transaction management (JCoServerTIDHandler):

boolean checkTID(com.sap.conn.jco.server.JCoServerContext arg0, java.lang.String arg1);
void confirmTID(com.sap.conn.jco.server.JCoServerContext arg0, java.lang.String arg1);
void commit(com.sap.conn.jco.server.JCoServerContext arg0, java.lang.String arg1);
void rollback(com.sap.conn.jco.server.JCoServerContext arg0, java.lang.String arg1);

IDOC-Handling (JCoIDocHandler):

void handleRequest(com.sap.conn.jco.server.JCoServerContext arg0, com.sap.conn.idoc.IDocDocumentList arg1);

There's only checkTID with a return value. No method has a throws declaration.

How to tell the calling SAP-System that e.g. commit/confirmTID or handleRequest failed ?

Throw a runtime exception ? What happens afterwards, does SAP resend the IDOCs or restart the transaction ?

Is there any documentation how to handle these error situations ?

Any help is welcome, if my description is unclear or incomplete, please don't hesitate to ask.

Thanks a lot.