Re: Oracle 10 Failover

From: Chris Seidel <>
Date: Thu, 11 Sep 2008 11:45:17 +0200
Message-ID: <48c8e8ab$0$6666$> wrote:

> Dataguard can be configured in various protection modes.
> One of them guarantees a commit on the primary will only execute if
> the corresponding commit in the standby succeeds.
> This means you should be able to guarantee zero-loss.

Ah ok.

> Using replication techniques you have no control over this, as Streams
> etc replicate changes on table level, it doesn't work on transaction
> level.

So DG in synchronous mode is on tx-level. And DG on asychronous mode is much easier the handle (setup, monitor, etc) because it's on database level, not on table level.


>> OK, so you advice that one should use DG and not replication/streams
>> to create a failover/standby server?
> You need to answer whether you can afford data loss (or inconsistent
> data) and how much down-time you can afford.
> Apart from that you need to take into account Streams and other
> options potentially require more manual intervention and are more
> difficult to troubleshoot.

Hm. For a standby database I now cannot see any why to use replication/streams instead of DG.
Are there any reasons?

> A completely different idea, and sorry I don't recall the product name
> right now (it was an EMC product), is to replicate the disks, so
> outside the database.

Hm, it can replicate open redo logs?

> No, for me you have a distributed environment when you have two
> *independent * databases which share data.
> Let' s assume you have two different applications in two different
> databases, both share 'reference data'
> This can be accomplished by database links, it can be accomplished by
> .. Streams etc. Actually *this* is the purpose of Streams.

OK, understand.

> A physical standby database isn't fully accessible, and doesn't
> function without the primary. Even if they may be in two different
> locations, they are not independent, so this is not a distributed
> environment.

OK. Makes sense ;)

Thank you Received on Thu Sep 11 2008 - 04:45:17 CDT

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