On Thu, Apr 22, 2004 at 09:42:12AM -0400, Eric Comeau wrote: > > What is Oracle selling as their replication solution these days? [. . .] > Their ORAC if I understand it correctly is a "cluster" solution and > no a "replication" solution. This is an example of why I think most of the discussion about "replication" is so confusing. ORAC is certainly a kind of replication: it provides always-on, hot redundancy in a cluster of machines. It's multi-master, and something very close to asynchronous. It's a _very_ clever system, but it'll do you not one whit of good if your primary site fails. Also, it's not suitable for use on unreliable hardware: every cluster member failure causes a "remastering" event which causes everything to stop while remastering happens. Finally, it requires some nifty but expensive storage -- storage which itself could be a single point of failure, if it failed in the right ways. To solve all of that, Oracle also offers Data Guard. This is basically a standard log-shipping technique. The off-site "standby" databases can't be used while in standby mode. This has all the standard caveats of asynchronous WAN replication, not least of which is that if you processed a $100 million transaction right before your master failed, and then you recovered onto a slave which didn't have that last moment of data, you might find yourself making a $100 million mistake. So, Oracle Corp offers two different ways to keeo you up nights. :) I'm sure they're both wonderful products. But they certainly don't have a one-size-fits-all approach. A -- Andrew Sullivan | ajs@crankycanuck.ca ---------------------------(end of broadcast)--------------------------- TIP 7: don't forget to increase your free space map settings
