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Here are three ways to look at it.
Streams is considered an "Integration" product.
Data Guard is considered a "High Availability" product.
RAC is considered a "Scalability" product.
2) logical vs. physical
Streams (and the similar SQL-apply based Logical Standby) is logical, Data Guard Physical Standby is, well, physical. RAC is either physical or both, depending on your precise definition. (I guess when we have cross-platform RAC, then it will be logical...)
3) instance vs. storage
RAC protects the instance. Streams protects the storage (but that is not its primary purpose). And Data Guard does both (as long as you can accept a brief outage of your instance).
(this overlaps with some of Pete Sharman's comments quoted below).
-Mark Bole
Ranko Mosic wrote:
> Correction: above mentioned proc is DBMS_STREAMS_ADM.MAINTAIN_SCHEMAS
> ( only for 10.2 ).
> Streams is Oracle's official replacement for Adv. Replication.
> RAC, Data Guard ( standby), Streams( Adv Repl), can all be considered (
> partially ) as HA solutions and in that sense
> they are interchangeable.
> Standby can be in the same cage as primary so it is not only for site
> protection.
>
> Regards, Ranko.
>
> On 11/12/05, Pete Sharman <peter.sharman_at_oracle.com
> <mailto:peter.sharman_at_oracle.com>> wrote:
>
> Nope I disagree with your comment on Streams being an alternative to
> RAC. Nor is advanced rep. They solve totally different problems –
> RAC is for protection from machine failure (and scalability on the
> other side of the equation), Streams and advanced replication are
> for data distribution and protection from site failure (this last
> aspect also being something that DataGuard resolves). Some people
> (who I also disagree with) are saying that RAC with extended
> clusters can solve the site failure issue as well. So if anything,
> there is a possible argument that RAC can be considered an
> alternative to Streams, but not the other way around. J
>
>
>[...]>
> <mailto:oracle-l-bounce_at_freelists.org>] On Behalf Of Ranko Mosic
> Sent: Sunday, 13 November 2005 2:04 AM
> To: gorbyx_at_gmail.com <mailto:gorbyx_at_gmail.com>
> Cc: Oracle-L Freelists
> Subject: Re: "Oracle Streams" by Madhu Tumma
-- http://www.freelists.org/webpage/oracle-lReceived on Sun Nov 13 2005 - 19:19:13 CST