Re: dataguard = Rac and/or Standby for 10G
- From: Carel-Jan Engel <cjpengel.dbalert@xxxxxxxxx>
- To: kduret@xxxxxxxxxxxxxxxxxxxx
- Date: Fri, 10 Sep 2004 01:33:24 +0200
Hi Kathy,
What platform are you using? Data Guard is available for 8i on AIX,
HP/UX and Solaris. It's merely a set of scripts, but installation,
instantiation and management works pretty well. It performs automatic
datafile creation on the stanby server (by parsing the alert<SID>.log
file!). Data Guard for 8i does atomatic gap detection of missing
logfiles on the standby as well, and will automatically close the gap.
This comes into place when the standby has been down or unreachable for
some time. DG/8i might help you immediately, and it's downloadable from
OTN for free.
Data Guard on 9i works very well, expecially Physical Standby. It cost
no no extra dollars (if you have Enterprise Edition). You are running
standby right now, so you must have licensed your standby server as
well. If not, it's gonna cost you an extra license. However, I've seen
deals of 25% of the listprice for the standby, or even for free.
I've done quite a lot of installations through Europe, starting with
9.0.1. (I'm working as an independent contracter). If you have Data
Guard, and you can afford a short outage at a disaster, you're better of
than with RAC. RAC doesn't give you a redundant database, doesn't give
you the opportunity to set a DELAY in applying logfiles (mind they are
sent en stored at the standby, just not applied). This delay is
especially usefull to recover from logical errors e.g. dropping a
table. Data Guard for 8i gives you the possibility of delaying some
number of logfiles, 9i gives you a delay measured in time. Both give you
the ability for gracefull switchover, which leaves your primary intact,
and the ability of putting your standby in Read Only mode.
Your decision about the binaries make a lot of sense for a DG
configuration. When I install patches I never go along Oracle's DG
special instrunctions to patch both databases simultanuously. In stead
of that I shutd down the standby, and patch the primary. Acting this
way, the standby gives me a fallback scenario. After succesfull putting
the primary live again, I perform an instatiate of the standby. During
the patch I create a cold backup using the standby, minimizing downtime.
When you put all binaries in a central location, this method will only
work when you create a new ORACLE_HOME for every patch. Keeping the
binaries local avoids this problem. (Although I see no problem in
creating a new ORACLE_HOME for every patch, expecially when you run more
instances on the same server)
I hope this helps,
Best regards,
Carel-Jan Engel
===
If you think education is expensive, try ignorance. (Derek Bok)
===
On Thu, 2004-09-09 at 18:12, Duret, Kathy wrote:
> Is anyone using Dataguard? Is it worth the extra $$. We are still firmly
> on the fence as to whether we are going 10G Rac or just 10G. We are not a
> true 24/7 shop and our applications are not
> ready for Rac or Standby (i.e. they would have to be restarted) so I am
> wondering if I should bother with dataguard or not. We have standby for 8i
> now and just wondering if dataguard is worth it.
>
> I plan to test drive 10G dataguard, I was just wondering what others
> thought.
>
> Oh, and we decided to keep the binaries local for the oracle home instead of
> on the San. We couldn't find a compelling reason either way for us. We
> would not have plenty of room on the SAN so we would not have had to buy
> more storage (yet any way). The internal / san time was the same. We
> really didn't have that much hitting the binaries.
>
> Kathy
>
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