Re: Log Switches in RAC

  • From: Surachart Opun <surachart@xxxxxxxxx>
  • To: Rajesh Rao <Rajesh.Rao@xxxxxxxxxxxx>
  • Date: Wed, 11 Nov 2009 02:13:52 +0700

Sorry Email...

About log switch, If don't use force switch log "alter system archive log
current" and ...etc

Normally, log switch (if have 3 groups) -> oracle will write log file group1
, and when it gets to the end of this set of files, it will switch to log
file group2 ,and then group 3... and switch back to group1. So, A log switch
on one instance of a RAC does not trigger log switches across one or more of
the other instances.

But if we use "archive_lag_target" initialization parameter, that will make
all instances switch in the same time.
http://download.oracle.com/docs/cd/B19306_01/server.102/b14237/initparams009.htm

archive_lag_target -> oracle recommends for RAC (Multiple instances should
use the same value)

SQL> show parameter archive_lag_target
NAME                                 TYPE        VALUE
------------------------------------ -----------
------------------------------
archive_lag_target                   integer     3600


Surachart Opun
http://surachartopun.com


On Wed, Nov 11, 2009 at 1:33 AM, Rajesh Rao <Rajesh.Rao@xxxxxxxxxxxx> wrote:

>  Sorry, I mean, other than the alter system commands, Why and when would a
> log switch on one instance of a RAC trigger cause log switches to happen
> across one or more of the other instances?
>
>
>
> *From:* Surachart Opun [mailto:surachart@xxxxxxxxx]
> *Sent:* Tuesday, November 10, 2009 1:24 PM
> *To:* Rajesh Rao
> *Cc:* oracle-l@xxxxxxxxxxxxx
> *Subject:* Re: Log Switches in RAC
>
>
>
> If you are meaning switch log by manual...
>
>
>
> "alter system switch logfile"
>
> This command switches log on that instance.
>
>
>
> "alter system archive log current"
>
>
>
> This command switches log all instance in RAC
>
>
>
> Example:
>
> SQL> alter system switch logfile;
>
>
>
> System altered.
>
>
>
> SQL> alter system archive log current;
>
>
>
> System altered.
>
>
>
>
>
> Good Luck
>
> Surachart Opun
> http://surachartopun.com
>
>  On Wed, Nov 11, 2009 at 1:11 AM, Rajesh Rao <Rajesh.Rao@xxxxxxxxxxxx>
> wrote:
>
>
>
> Why and when would a log switch on one instance of a RAC trigger cause log
> switches to happen across one or more of the other instances?
>
>
>
> Thanks
>
> Raj
>
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