Designed to "facilitate easy global sharing of PNR data," the CRS-GDS companies "function both as data warehouses and data aggregators, and have a relationship to travel data analogous to that of credit bureaus to financial data.".[3] A canceled or completed trip does not erase the record since "copies of the PNRs are ‘purged’ from live to archival storage systems, and can be retained indefinitely by CRSs, airlines, and travel agencies."[4] Further, CRS-GDS companies maintain web sites that allow almost unrestricted access to PNR data – often, the information is accessible by just the reservation number printed on the ticket.