Re: Dataguard setup at DR site
Date: Sat, 25 Apr 2009 17:49:28 -0700
If you don't force logging in the primary and you have non-logged transactions in the primary, those transactions will not get to the standby (because they're not in the logs, of course) and you'll have physical (or is it logical?) corruption in the standby. However, you won't know it until you open the standby and try to query tables where transactions are missing. That's why forced logging is a prerequisite for setting up a physical standby.
Learned this one the hard way.
On Sat, Apr 25, 2009 at 2:48 PM, Howard Latham <howard.latham_at_gmail.com>wrote:
> DG evolved from 'log shipping' and need not exist now. It does provide
> extra features and it does TRY and manage
> everything for you but you can have a 'data guard' setup without dataguard.
> I was tld itit sorts out network failures etc for you and
> probaly the tools it gives you are worth it. I imagine that auditors might
> prefer a proper DG setup ?
> Coments anyone?
> 2009/4/25 Kumar Madduri <ksmadduri_at_gmail.com>
> ---------- Forwarded message ----------
>> From: Kumar Madduri <ksmadduri_at_gmail.com>
>> Date: Sat, Apr 25, 2009 at 1:13 PM
>> Subject: Re: Dataguard setup at DR site
>> To: asif_oracle_at_yahoo.com
>> Cc: Oracle-L_at_freelists.org
>> Thank you Asif.
>> I read about cascading databases. But my question was, does it really
>> matter how the original standby is constructed (in my case I am not
>> using DG to build the standby). Even in this case can I cascade from
>> my standby to my DR standby (which I am planning to set it up using
>> DG). Theoritically it should be fine.
>> In that case, can I disable force loggin on production and enable
>> force logging on standby only. That way I would minimize any
>> performance impact.
>> So primary no force logging > standby (using old method of applying
>> redo) has force logging . THis is used as source for standby on DR
>> site (which will use DR).
>> Thank you
>> - Kumar
>> On Sat, Apr 25, 2009 at 1:03 PM, Asif Momen <asif_oracle_at_yahoo.com>
>> > Dear Kumar,
>> >>> Is it possible to use the cascade standby approach in this scenario?
>> > Yes, you can have cascaded physical standby databases (I think you can
>> go up
>> > to 9 cascaded standby databases)
>> >>> Based on the real world experience, how much of a performance impact
>> >>> would it be if force logging is enabled?
>> > The answer is, "it really depends". In an OLTP environment you would
>> > little to no whereas in a data warehouse env you may have huge gains.
>> > You may have nologging operations performed on the primary yet keeping
>> > standby database in sync.
>> > Regards
>> > Asif Momen
>> > http://momendba.blogspot.com
>> > --- On Sat, 4/25/09, Kumar Madduri <ksmadduri_at_gmail.com> wrote:
> Howard A. Latham