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RE: ZERO Database Downtime???

From: Carel-Jan Engel <>
Date: Wed, 29 Mar 2006 21:38:23 +0200
Message-Id: <>

About 10 months ago the same topic came along at another list. This was my answer (slightly edited for this list and this year):

> I had an interview with Ken Jacobs, some years ago, and another one
> September 2004, and both times asked him when Oracle will support
> Rolling Upgrades. The first time he told me they were working on it,
> and in September 2004 he elaborated on the subject and told me there
> are rolling upgrades now.
> 'Almost', I answered. The fact that SQL-Apply means there are two
> independent databases, in stead of 'clones' as in Physical Standby,
> means that there is no Transparent Application Failover, or even
> Translucent Application Failover (thank you Pete Sharman). It means
> that the application has to be restarted/coalesced/interrupted
> whatsoever (or whatever nice marketing speak you can invent to hide
> the true meaning). So, there is NO rolling upgrade. Period.
> Ken agreed.
> They get close, but there are so many pitfalls and tiny small
> problems. What if the application relies on rowid's? They're different
> in two independent databases. All there is the whole complexity of
> maintainting a Logical Standby, with unsupported datatypes and
> unsupported DML commands. There is the scaleability problem of
> SQL-Apply. There is the need for supplemental logging on the primary.
> If the whole RAC-setup is created with scaleability in mind, how to
> cope with the single instance SQL-Apply part? It probably cannot keep
> up with the rest of the system. Apart from that, it supports one-off
> patches only, not patch sets (or has that changed already?).
> I do not follow the Meta Link approach of upgrading Data Guard
> environments in their connected state. I use to defer the redo
> forwarding while upgrading the primary. After the primary is patched
> succesfully, and tested, and restarted, I reinstatiate the standby.
> Keeping the standby connected jeopardizes the whole conecpt of HA, in
> my opinion. If the patch process fails for some reasons, you end up
> with two unusable databases. My approach gives the possibility of
> activating the standby immediately after the patch fails, while
> postponing the patch process to a later moment, after more testing.
> Just my $0.02

Best regards,

Carel-Jan Engel

If you think education is expensive, try ignorance. (Derek Bok) ===

On Wed, 2006-03-29 at 11:21 -0800, wrote:

> For a while they were saying that a Shared Oracle Home
> for RAC was a bad idea because "you can't do a rolling upgrade"
> with a single shared Oracle Home. Then people started calling them
> on the fact that you can't do a rolling upgrade AT ALL without
> Data Guard involvement...
> marketing
> >>>-----Original Message-----
> >>>From:
> >>>[] On Behalf Of Michael Fontana
> >>>Sent: Wednesday, March 29, 2006 10:35 AM
> >>>To: Jared Still;
> >>>Cc:;
> >>>Subject: RE: ZERO Database Downtime???
> >>>
> >>>Excuse me, but "little or no" is not the same as "Zero Downtime".
> >>>
> >>>A logical SQL apply is also not feasible in a large
> >>>installation, or if there is complexity, such as RAC.
> --

Received on Wed Mar 29 2006 - 13:38:23 CST

Original text of this message