RE: Converting from physical to logical standby
- From: Carel-Jan Engel <cjpengel.dbalert@xxxxxxxxx>
- To: sorr@xxxxxxxxxxxx
- Date: Wed, 29 Sep 2004 21:50:40 +0200
Hi Steve,
Creating LSB from scratch DOES need a coalesce of the primary. So, it is
inaccessible for a couple of minutes.
My reply on your follow-up question: what version do you have in mind?
I've worked with both PSB and LSB. One LSB in production, and that has
been abandoned (it was a mixed setup: two LSB's for publishing web
content and one PSB for the content management system. It was a
newspaper). PSB on many sites, and quite succesfull. I notice a slight
change in naming LSB by Oracle: It's called SQL Apply many times now. It
might hint you to the fact that it isn't actually a Standby Solution. In
my honest opinion it is not, at least not in 9iR2. Ita has many
restrictions, and many failures/wrong datatypes/wrong SQL can stop it,
leaving you with the job to resync the thing.
Doing RMAN backups on the standby is officially supported, I haven't
done it though. One reason to create your backups on the primary might
be that relying on the standby for backups is chaining the
backup-process: when the standby fails your backup will fail likewise. I
don't like SPOFs.
Best regards,
Carel-Jan Engel
===
If you think education is expensive, try ignorance. (Derek Bok)
===
On Wed, 2004-09-29 at 17:36, Orr, Steve wrote:
> Thanks.
>
> RE
> > converting PSB to LSB is not possible.
> What about creating LSB from scratch... Can it be done without making
> the primary inaccessible?
>
> Follow up question... Anyone have much experience with LSB vs PSB? I
> know PSB performs better but is LSB just as dependable? If performance
> is okay with LSB is it otherwise just as good as PSB?
>
> Performing a full export on the primary could impact performance but
> could be quite suitable on a standby. One possible advantage of LSB is
> that you don't have to toggle the recovery/database open status.
>
> Other thoughts on PSB vs. LSB? Any reason whatsoever not to perform RMAN
> backups on the standby?
>
>
> Standing by...
> Steve Orr
>
>
>
> -----Original Message-----
> From: oracle-l-bounce@xxxxxxxxxxxxx
> [mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of Carel-Jan Engel
> Sent: Tuesday, September 28, 2004 11:58 PM
> To: DWILLIAMS@xxxxxxxxxxxxx
> Cc: 'oracle-l@xxxxxxxxxxxxx '
> Subject: RE: Converting from physical to logical standby
>
>
> Steve,
> For 9iR2 I attempted to extend my instatiate scripts for Physical
> Standby (PSB) with Logical Standby (LSB) capabilities. It actually
> worked, using vanilla hot backups.....4 out of 5 times. The quiesce
> database is still needed, although it didn't take too long. So, no major
> outage/standstill was needed. But, a real instantiation 'on the fly' is
> not possible. AFAIK converting PSB to LSB is not possible.=20
>
> Whenever the script failed, for no obvious reason the next run went OK
> most of the times. I haven't put too much effort into solving this,
> because of the instability and restrictions of LSB, and lack of demand
> for LSB. I'm a poor self-employed contractor ;-)
>
> Best regards,
>
> Carel-Jan Engel
>
> =3D=3D=3D
> If you think education is expensive, try ignorance. (Derek Bok) =
> =3D=3D=3D=20
>
>
>
> On Tue, 2004-09-28 at 19:02, DENNIS WILLIAMS wrote:=20
>
>
> Steve - In answer to question #2, Robert Freeman on page 417 of Oracle9i
> RMAN Backup & Recovery says "RMAN backups cannot be used to create a
> logical Standby database, because RMAN cannot quiesce a database".
> =20
> Dennis Williams
> DBA
> Lifetouch, Inc.
>
>
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