[Oracle-l] Why extra standby redo log group?

Here is an example form one of my standby databases
GROUP#,DBID,THREAD#,SEQUENCE#,BYTES,USED,ARCHIVED,STATUS,FIRST_CHANGE#,FIRST_TIME,LAST_CHANGE#,LAST_TIME

5,2993939164,1,539739,1258291200,512,YES,ACTIVE,124541122419,4/5/2009 11:15:20 AM,124541122522,4/5/2009 11:15:20 AM
6,2993939164,1,539738,1258291200,294810112,NO,ACTIVE,124540991837,4/5/2009 11:03:59 AM,124541122419,4/5/2009 11:15:20 AM
7,UNASSIGNED,1,0,1258291200,512,NO,UNASSIGNED,0,,0,
8,UNASSIGNED,1,0,1258291200,512,NO,UNASSIGNED,0,,0,
9,UNASSIGNED,1,0,1258291200,512,NO,UNASSIGNED,0,,0,

As you can see both are active but one is archived=yes the other is not sicne it is a realtime recieve . in a very busy environment you will see all unassigned as Active with one being used as realtime till time that the backlog is more than the standby redo logs.

Original Message ----
From: Yong Huang
To: john.hallas_at_morrisonsplc.co.uk; fuadar_at_yahoo.com; Martin Brown
Cc: [email protected]
Sent: Sunday, April 5, 2009 9:39:09 AM
Subject: RE: Why extra standby redo log group?

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 wrote:

From: Martin Brown
Subject: RE: Why extra standby redo log group?
To: john.hallas_at_morrisonsplc.co.uk, fuadar_at_yahoo.com, yong321_at_yahoo.com
Cc: [email protected]
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.
that the standby can keep up with the primary. It is only a
recommendation though and not mandatory
On Behalf Of Fuad
Arshad
to cover for backlogs I.e Log switching is faster than the
standby instance can perform