PmsXchange will transfer reservations to a property management system (PMS) using a PULL based model. The PMS should use OTA_ReadRQ with a selection criteria to request reservations, modifications or cancellations and OTA_NotifReportRQ to confirm that a reservations, modifications or cancellations has been processed.

It is currently only possible to query undelivered reservations per hotel. Undelivered identifies all reservations, modifications or cancellations which have not been previously acknowledged with an OTA_NotifReportRQ message by the PMS.

The exchange involves 5 different messages: 

1. Using the OTA_ReadRQ message, the PMS will request reservations, modifications or cancellations from pmsXchange.
2. Using the OTA_ResRetrieveRS message, pmsXchange will return reservations, modifications or cancellations which meet the requested criteria.
3. The PMS will process the response and send an OTA_NotifReportRQ with success or errors after processing. 
4. PmsXchange will then respond with an OTA_NotifReportRS to acknowledge the receipt.
5. Using the OTA_HotelAvailNotifRQ, the PMS sends pmsXchange back the affected 'Availability' change.

General Guidelines for Reservation Retrieval

These guidelines must be followed by all connecting property management systems.

• The PMS should pull reservations every 2-5 minutes . In other words, reservations/modifications/cancellations should not be requested more often than every 2 minutes (Ex: every 1 min) and less often that every 5 minutes (Ex: every 10 mins).
• After the PMS has retrieved a reservation, modification or cancellation, the PMS must send a notification message to pmsXchange to acknowledge that the reservation has been received. This message can notify pmsXchange either of successful processing or that the processing failed. 

Availability (@BookingLimit) Updates after Reservation Delivery

The integrated PMS MUST return the reduced 'Availability' (@BookingLimit) value via the Inventory API immediately after a reservation has been delivered. The Channel Manager will not process inventory changes for 'Cancel' or 'Modify' status reservations. For modified or cancelled reservation, it is expected that the integrated PMS will pass back 'Availability' changes once the modification or cancellation has been processed.