Re: Best practice for Dataguard in 10g?
- From: Nuno Souto <dbvision@xxxxxxxxxxxx>
- Date: Mon, 07 Sep 2009 18:17:41 +1000
Vishal Gupta wrote,on my timestamp of 6/09/2009 10:45 PM:
LGWR for redo log shipping. If there is too much redo generation at any
point in time which your network is not able to cope with, then log
shipping will switch from LGWR to ARC automatically. And it will revert
back to LGWR automatically when it catches up with latest redo
generation.
That's excellent news indeed. I wasn't aware that ARCH
would kick in. That is indeed good news.
But if you are generating 500GB/day or 355MB/min on average. Then
depending on your redo log size and log switching frequency. Using ARCH
will also not harm you. It depends on how much data you are willing to
use in case of primary DW failure. And when you can regenerate
missed/lost data from your OLTP.
We generate 500GB/day but it's peaky, not constant.
Ie: there are peaks of redo generation where we
switch 1GB redo logs in less than a minute, then
it slows down to a much more sedate rate of one switch
every 15 minutes or so, and even longer idle periods.
There will be *some* data loss even by using LGWR unless you are using
SYNC and AFFIRM options, which you would not want to use to protect
against hanging primary database, which will occur during network
failure prevent redo log transfer.
Exactly. We can easily afford some data loss.
The ETL bursts are from external sources, with a staging
area for the transfered data. And all ETL operations
are atomic and logged/serialized by the application,
so we can always reconstruct from a given interrupt point
and identifying which it is is a piece of cake with the
application log.
Thanks heaps for the feedback, Vishal.
Much appreciated.
--
Cheers
Nuno Souto
in sunny Sydney, Australia
dbvision@xxxxxxxxxxxx
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