RE: Converting from physical to logical standby

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_at_freelists.org
> [mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Carel-Jan Engel
> Sent: Tuesday, September 28, 2004 11:58 PM
> To: DWILLIAMS_at_LIFETOUCH.COM
> Cc: 'oracle-l_at_freelists.org '
> 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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