Re: Standy database / RMAN

  • From: Manjula Krishnan <oradba_la@xxxxxxxxx>
  • To: oracle-l@xxxxxxxxxxxxx
  • Date: Thu, 2 Sep 2004 11:28:01 -0700 (PDT)

Thanks for the info Carel.
I was thinking of logical standby because I wanted to offload running reports 
to the standby. But, on reading the docs further, I will not be able to use 
logical standy because of the datatype restrictions etc.
By 'one of our servers' I meant I have several Oracle d/s servers and I was 
trying on one of them first. And no, the standby will not be on the same server 
as primary.
And since DG is your speciality, I will ask this question again: what happens 
when I have to apply patches. Is it as simple as shutdown primary & standby, 
applying the patches and startup again? 
Carel-Jan Engel <cjpengel.dbalert@xxxxxxxxx> wrote:
On the RMAN topic others can advise you better than I can. Data Guard
(DG) is my cup of tea.

Why are you choosing Logical Standby (LSB)? It has quite some
restrictions, and IMHO this is not reliable enough for High Availability
(HA) purposes. LSB takes more resources on the primary, because
additional logging has to be written to enable the standby to
reconstruct the SQL. One wrong transaction or data type will break the
SQL Apply process, and creates the need to manually fix the problem (if
possible at all) before you can continue. Another thing is you mention
'one of our servers'. I presume this doesn't mean that you are going to
run both instances/databases on the same server, do you? That wouldn't
add too much to your redundancy/availability. If you want HA, go for
Physical Standby (PSB). LSB consumes far more resources on your standby
server, it has to reverse engineer SQL from the redo information and the
execute it, generating redo and all the overhead of updating indexes
again. No problem if your LSB server is just there in case of, but
people tend to make it useful by loading other tasks on the server. 

Bottom line:
- RMAN: go for it
- Data Guard: fine, but for HA use PSB, not LSB

Best regards,

Carel-Jan Engel

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

On Wed, 2004-09-01 at 17:37, Manjula Krishnan wrote:

> Hi:
> I want to implement both 9i Data Guard and RMAN on one of our servers (AIX 
> 5.2, Oracle 64 bit). This server is in the process of being tested. 
> It will go into production sometime in October. Hot backups are currently 
> being performed nightly (just with scripts no RMAN). 
> 1. I want to setup RMAN. How easy or difficult is it to switch from these 
> scripts to using RMAN?
> 2. I also want to implement logical standby for max availability. 
> -- When the data is refreshed for going live, will it affect the logical 
> standy in any way. I think I will have to recreate it.
> -- What about RMAN? How will the backups using either RMAN or the scripts 
> affect the standby?
> I am reading the Oracle DataGuard (rel 9.2) on technet and other related 
> metalink documents.
> What else do I need to be aware of? Please point me to anything else you 
> think I should read before getting started.
> Thanks,
> Manjula
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