RE: Standby redo logs

  • From: "Mark W. Farnham" <mwf@xxxxxxxx>
  • To: <nassyambasha@xxxxxxxxx>, <justin@xxxxxxx>
  • Date: Thu, 31 Jul 2014 12:10:12 -0400

Good thread.


One additional point: SOMETIMES a standby is configured with an intentional lag 
in the application of the redo as a protection against logical corruption of 
your database by any of programming error, hacking attack, insider malfeasance, 
<and more than I can think of>. In that case lacking standby redo logs is 
useful to prevent accidentally starting the lagged (possibly remote) version of 
the database.


Another way to achieve this is flashback of some type, but a lagged standby 
*might* be easier to secure from outside attack. Combined with capture of the 
raw inbound transaction information, this essentially gives you a time machine. 
Having a time machine handy is very useful.


(Please notice none of this contradicted any of the very good suggestions about 
various ways of keeping things as close to zero loss as possible with varying 
levels of overhead. It merely raised a possibility regarding a different goal 
for the standby. The neat thing is that you can have both when that is the 
right thing to do.)




From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx] On 
Behalf Of Nassyam Basha
Sent: Thursday, July 31, 2014 2:23 AM
To: justin@xxxxxxx
Cc: napacunningham; oracle-l-freelists
Subject: Re: Standby redo logs


Yes, I forgot to add that point regarding data loss. There is no such zero data 
loss with maximum performance. But if you configure FAST SYNC then you can get 
almost and maximum zero data loss with maximim performance until unless rare 
situations.. its called catastrophic failure.


On Thu, Jul 31, 2014 at 8:53 AM, Justin Mungal <justin@xxxxxxx> wrote:

Be careful with your wording, because even with standby redo logs you can't 
ensure zero data loss unless you're running in maximum protection mode. 


I would recommend configuring standby redo logs because instead of applying 
redo in batches as archive logs arrive at the standby, you can use real-time 
apply (requires standby redo logs) to stream redo continuously to the standby. 
This generally lowers potential data loss and can also improve fail over times.


Oh, and while you're busy reading the docs... check out the Data Guard Broker 
if you haven't already...


On Wed, Jul 30, 2014 at 9:35 PM, Michael Cunningham <napacunningham@xxxxxxxxx> 

Are there dangers with not having standby redo logs in a 12c physical standby 
db? The docs do indicate they are necessary to insure zero data loss. Any other 
experience out there?

Michael Cunningham



Nassyam Basha. 

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