Re: Synchronous DB replication

On Thu, 13 Feb 2003 23:23:46 +0000, Ralf Fernan wrote:

> I was wondering about how widespread synchronous replication is, and also
> what is the alternative solution. I don't have a good grip of how critical
> conflicts can be resolved with asynchronous replication, when asynchronous
> replication is used. For example, in a financial transaction, I and
> somebody else (on my behalf )could overdraw my account by near-simultaneous
> withdrawals in different geographic locations. How would asynchronous
> replication work in this case?
>

I don't know about you, but I've been caught many times this way. Withdraw some cash from an ATM at noon... and a message flashes up that 'transactions will be processed the next business day', you forget, spend up big (thank you, Other Half!) and withdraw some more at 6.00pm. Wake up next morning, and discover you're over-drawn. So sometimes the conflict resolution method appears to be 'you're a responsible adult, you're supposed to know these things. And that will be $10 for a processing fee, thanks all the same!!'

The broader point is that of course asynchronous replication can introduce conflicts (I update EMP, setting Bob's salary to 800, you update it a bit later to 900. Which of us wins?)

There's a whole conflict resolution process to implement with asynchronous replication, and it basically has to be managed carefully, and the business rules defined appropriately.

When they've written DBMS_TELEPATHY, Oracle will of course be able to read your mind to work out what to do, but until then, it's down to you.

Regards
HJR Received on Thu Feb 13 2003 - 20:51:24 CST