Codeshare availability is phantom availability at day of departure. We often see availability for the codeshare flight number but zero availability on the true flight number. Also the reason agents need to call the OA is the OA flight can be oversold (i.e. no inventory) and still show availability in SHARES/Apollo. We can even book it and and get a holding confirm (HK) in our system but the booking never appears in the OA system.