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-   -   Simultaneous Submit to overcome Z1 inventory (https://www.flyertalk.com/forum/delta-air-lines-skymiles/1957672-simultaneous-submit-overcome-z1-inventory.html)

Colin Feb 22, 19 4:05 pm

Simultaneous Submit to overcome Z1 inventory
 
Trying to get two seats at cheapest J pricing with Z1 inventory.
Anyone have experience with ticketing one in each of two browsers with simulatenous submit?
DL.com and Expedia (via AMEX).

bj27 Feb 22, 19 4:16 pm

It won't work. One seat in Z = one seat in Z. You cannot magically make another Z seat appear with this trick...

Whichever browser is second to the finish line will most likely error out with the webpage displaying the fare has gone up.

rylan Feb 22, 19 8:43 pm

Yeah the DL system is smarter/faster than you can be in this case. One of the browsers will win and one will loose.

HWGeeks Feb 22, 19 8:52 pm

i had a similar issue happen before but I wasn't trying to simultaneously book. I guess I was just the slower of the two people. I called Delta up and they honored the price I was originally quoted. But ymmv

sdadept Feb 22, 19 9:08 pm


Originally Posted by Colin (Post 30810926)
Trying to get two seats at cheapest J pricing with Z1 inventory.
Anyone have experience with ticketing one in each of two browsers with simulatenous submit?
DL.com and Expedia (via AMEX).

I can't say too much, but having intimate knowledge of how the reservation code works, this is impossible. The inventory column is briefly locked while a reservation is made. First one in wins.

mnbp Feb 22, 19 9:14 pm

There's nothing that says once a Z ticket is sold, that the airline won't ever decide to add another seat to the Z bucket. Maybe in an hour, maybe in a day, maybe in a week. Maybe.

audio-nut Feb 22, 19 11:20 pm

If the TA has guaranteed sell then it would overbook Z. I doubt DL gives that to anyone other than maybe partner airlines though.

exwannabe Feb 23, 19 4:26 am


Originally Posted by rylan (Post 30811624)
Yeah the DL system is smarter/faster than you can be in this case. One of the browsers will win and one will loose.

Not that it helps OP, but I vote that IE loses 😎

3Cforme Feb 23, 19 5:16 am


Originally Posted by sdadept (Post 30811673)
I can't say too much, but having intimate knowledge of how the reservation code works, this is impossible. The inventory column is briefly locked while a reservation is made. First one in wins.

I'm interested in that mechanism. I have found itineraries (non-stop, so it's not a married segment thing) found by ITA Matrix that did not find inventory on delta.com or aa.com. But Orbitz has been able to ticket them at the ITA Matrix price, and tickets were honored for travel.

bennos Feb 23, 19 5:31 am


Originally Posted by sdadept (Post 30811673)
I can't say too much, but having intimate knowledge of how the reservation code works, this is impossible. The inventory column is briefly locked while a reservation is made. First one in wins.

I don't think you have to worry about disclosing proprietary information here, this is how any well written inventory management system (and any ACID compliant database system) will work. When attempting to update inventory, a write lock must be obtained on the inventory counter (and only one request can hold a write lock at any given time), then the value of the counter is verified (this is where Z might now = 0 if an almost simultaneous sale were to take place), then the value of the counter is updated, then the write lock is released and the sale processed.

bennos Feb 23, 19 5:36 am


Originally Posted by 3Cforme (Post 30812463)
I'm interested in that mechanism. I have found itineraries (non-stop, so it's not a married segment thing) found by ITA Matrix that did not found inventory on delta.com or aa.com. But Orbitz has been able to ticket them at the ITA Matrix price, and tickets were honored for travel.

There's a difference between searching for available inventory and booking it once found. It's entirely plausible that ITA has better searching algorithms than the airline websites (airline inventory searches are a notoriously difficult computational problem to solve), or that caches got in the way, or that the website had a bug, or that the website implemented a different search algorithm, etc. If for whatever reason the search doesn't find existing inventory then the frontend has no way to know to ask to book it.

GrayAnderson Feb 23, 19 6:42 am


Originally Posted by bennos (Post 30812498)
There's a difference between searching for available inventory and booking it once found. It's entirely plausible that ITA has better searching algorithms than the airline websites (airline inventory searches are a notoriously difficult computational problem to solve), or that caches got in the way, or that the website had a bug, or that the website implemented a different search algorithm, etc. If for whatever reason the search doesn't find existing inventory then the frontend has no way to know to ask to book it.

Book With Matrix actually helped me "shake" a cheaper fare loose a few weeks ago. DL was trying to quote me a higher rate than I was seeing. I called in, they could only see the higher fare, but Book With Matrix led me to the fare in question (which I was then able to book via Delta.com, much to my shock). Someone was probably querying inventory differently.

Of course, another time in the last few weeks I was also able to find a fare on Matrix and the agent was able to see it as well, so there was probably just a gremlin in the system.

3Cforme Feb 23, 19 6:57 am


Originally Posted by bennos (Post 30812498)
There's a difference between searching for available inventory and booking it once found. It's entirely plausible that ITA has better searching algorithms than the airline websites (airline inventory searches are a notoriously difficult computational problem to solve), or that caches got in the way, or that the website had a bug, or that the website implemented a different search algorithm, etc. If for whatever reason the search doesn't find existing inventory then the frontend has no way to know to ask to book it.

Thanks for the comments but I'm talking about the most basic of r/t itineraries: one segment in each direction, same marketing/operating carrier. If aa.com and delta.com can't handle that it's time to go back to marks on a chalkboard. I'm wondering if Orbitz was selling inventory from a cache that AA/DL had exhausted, and the carriers allowed the transactions to go through, anyway.

MSPeconomist Feb 23, 19 7:12 am

Some of these systems use somewhat outdated information for the search and then only verify real time inventory availability during the purchase step. This is why one sometimes sees the message that the fare is no longer available after it appears during a search. The alternative of setting aside inventory during the search would be less desirable, although I see this happening on other types of websites that sell restricted inventory and tell you that it's being held for you for a certain period of time. Starriott Bonvoy shows the time remaining, although apparently doesn't pull the inventory until you go past the search phase and begin to book the room. Eventbrite appears to set aside the tickets at an earlier stage (again showing you have much time you have to complete the transaction), although typically on that website there's no search and consider step as one goes there to purchase a ticket to some particular event.

In the famous "fraudulent" ticketing case of the AA elite who did searches to check likely upgrade availability. It was claimed that AA sets aside inventory and creates a PNR at a much earlier phase than other airline websites generally do.

TerryK Feb 23, 19 7:58 am


Originally Posted by Colin (Post 30810926)
Trying to get two seats at cheapest J pricing with Z1 inventory.
Anyone have experience with ticketing one in each of two browsers with simulatenous submit?
DL.com and Expedia (via AMEX).

There is no such thing as simultaneous submit in systems. Central database process requests sequentially, even if just by 1/1000000 of a second.


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