RE: Some Dataguard is good, lots more must be better? (specifically, when do most actual failovers really occur?)

  • From: Carel-Jan Engel <cjpengel.dbalert@xxxxxxxxx>
  • To: "oracle-l@xxxxxxxxxxxxx" <oracle-l@xxxxxxxxxxxxx>
  • Date: Wed, 20 Sep 2006 23:56:03 +0200

On Wed, 2006-09-20 at 17:07 +0000, Laimutis Nedzinskas wrote: 

> Now regarding DG with time lag. Well, it is not a good option for
> maximum data protection(as Oracle defines it.) At least I do not know
> how to protect redo logs in this mode. Which means that for maximum data
> protection you have to have a standby database which is in complete
> sync, i.e. running in maximum protection mode(at least most of the
> time.) BUT I am not sure if file system snapshot technique can achieve
> this either.

Maybe the delay concept confuses you a little. Maximum protection and
Delay actually go together very well.!
Maximum protecion gurantees that redo is written at the standby at the
time the commit finishes. 
Delay allows you to wait a certain amount of time to apply the redo.

So, all redo IS protected in maximum protection mode, even if a delay is
configured. The standby can be in read only mode and still protect your

Best regards,

Carel-Jan Engel

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

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