Each request to GP Travel HUB has to identify particular booking to be processed. For that purpose special unique identifiers are used.

You should store the necessary identifiers received from a response in your application, to be able then pass it to request on the next step.

There are identifiers that are used on different request/response chains.

14.1.1. RAILRESERVATIONIDS

14.1.2. BOOKINGCODE

14.1.3. TRANSACTIONIDENTIFIER