RE: Why extra standby redo log group?

  • From: Yong Huang <yong321@xxxxxxxxx>
  • To: john.hallas@xxxxxxxxxxxxxxxxxx, fuadar@xxxxxxxxx, Martin Brown <martinfbrown@xxxxxxxxxxx>
  • Date: Sun, 5 Apr 2009 07:39:09 -0700 (PDT)

Martin, John, Fuad,

Thank you. When you have heavy transaction for a period of time, if you have n 
log groups on primary and n+1 SRL groups on standby, do you see all n+1 SRL 
groups used? That is, on the standby, do you see all, not just n, rows in 
v$standby_log under status column, alternately showing 'ACTIVE'?

I know if I manually switch logfile on primary, only n SRL groups will be 
'ACTIVE' (the extra stays unused). I'll test by building a small data guard 
where primary is on a node with fast storage and standby with slow storage and 
create lots of redo.

Yong Huang

--- On Sun, 4/5/09, Martin Brown <martinfbrown@xxxxxxxxxxx> wrote:

From: Martin Brown <martinfbrown@xxxxxxxxxxx>
Subject: RE: Why extra standby redo log group?
To: john.hallas@xxxxxxxxxxxxxxxxxx, fuadar@xxxxxxxxx, yong321@xxxxxxxxx
Cc: oracle-l@xxxxxxxxxxxxx
Date: Sunday, April 5, 2009, 8:46 AM

Totally agree. Our configuration has 8 primary nodes and (of
course) only 1 standby node. For those that don't run
DataGuard 10g, you can only have 1 active standby node.
Normal log switches happen about 3 per hour. During peak
times, our log switchs pick up speed and this configuration
keeps up quite nicely. 
> From: John.Hallas@xxxxxxxxxxxxxxxxxx
> To: fuadar@xxxxxxxxx; yong321@xxxxxxxxx
> CC: oracle-l@xxxxxxxxxxxxx
> Date: Sun, 5 Apr 2009 14:33:16 +0100
> Subject: RE: Why extra standby redo log group?
> I would agree with what Fuad says, it is to ensure
that the standby can keep up with the primary. It is only a
recommendation though and not mandatory
> John
> -----Original Message-----
> From: oracle-l-bounce@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of Fuad
> Sent: 04 April 2009 03:44
> To: yong321@xxxxxxxxx
> Cc: oracle-l@xxxxxxxxxxxxx
> Subject: Re: Why extra standby redo log group?
> Well in my case I've seem standby redo logs used
to cover for backlogs I.e Log switching is faster than the
standby instance can perform


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