Re: Changing isolation level? ++ scenarios

"mcstock" <mcstock @ enquery .com> wrote in message news:<KuOdnRWSp6I0oVKi4p2dnA_at_comcast.com>...
>
> if we're talking OLTP, which i think we all are, the data change
> continually, so it's really a matter of timing -- one isolation level tells
> me i've got 30, the other tells me i've got 50, but neither figure is
> reliable after it is read unless i decide to lock something:
>
> consider the following scenarios:

<snipped several scenarios>

Solution to all of thess scenarios is simple. You should just buy more ixixs, if there is so big demand for them. As I know reality in these kind of systems, solution is that number of available ixixs is never a hard limit, but a soft one. You will tell your customer: "Sorry, we do not have your ixixs in the local warehouse, but we bring them from ... in no time". All shops do it this way. With some exceptions, such as winner of x-mas most demanded present contest, you can usually get any goods quite quickely. In fact the biggest problem for markets is not "I have no ixixs available", but "what the hell will I do with all of these f**king ixixs I've ordered and no one wants them now?"

However, back to root of the problem. If you think about all of your scenarios, it can't be solved by any tool. It is not a technical problem, but a business one. How will you handle the easiest situation, rare stock with first time first serve basis (no prioritization)? Sounds simple, but think about next discussion:

When the transaction is started? Of course, when I'm selling to customer.

OK, but when is the exactly point when real sell begun? When customer want to buy a product, not just talk about it.

OK, but how will you know the customer really want to buy it? He will tell me.

OK, but will he ask if the product is available before or after?

Uh, usually before ...

<rest is obvious>

So as I see it. These scenarios are not about locking, isolation levels, Oracle, DB2 or whatsoever. This is primarily an complicated business issue and how to handle it depends on your business requirements and willingness of business to make trade-offs.

--
Dusan Bolek