Re: Sizing Redo log files
Date: Tue, 26 Jun 2012 23:09:14 -0500
Message-ID: <CA+O6cLJVYizNt=NN68zfrXr3mozBGZUMaSMNx-gqYz05j13PKg_at_mail.gmail.com>
Looks like the math is wrong (as you feared). If the system fills up those redo logs faster than archiver, then it is an issue.
In other words, if archiver is slower ( and txn rate is faster than that) , then it is an issue.
- Below I am trying to parse your words -----------------
"the time required to cycle through all (N-1) redo files" => Rate of redo generation to fill up N-1 redo logs (volume of txn) "time it takes to have the archivelogs created for (N-1) redo logs" => Not sure , as it can probably mean just one redo log .
Here is a scenario (for beginngers only) I have 5 redo logs , completed the 5th redo and cycled back to 1 now. So 1 is CURRENT, 5 is just completed.
*
1---2---3---4----5
Assuming, archiver already finished its job for 2,3 and 4 and has started
working on 5th..,while CURRENT redo is at 1... and the system is
experiencing
sudden burst of txns.. and redo logs 2,3 are filled up faster, 4 is nearly
filled up.
Now if archiver is struck on archiving the 5th redo, then system has to
wait for its (archival) completion before using it.
This can very well happen if the archive-log dest is poorly configured ,
and so this issue may be avoided by allocating more redo logs (=> txn
volume).
- -----------------------------------
I re-read the message a few times to understand it correctly ...giving a pause/break at the right place (and Im not a native English speaker) I am also tired and its past 10.40 pm, I like the 'mathematical way of saying things..just for the kick of it :-) ' and took it as a small challenge (to prove that some piece is missing)
Cheers,
Vasu
From: Jared Still <jkstill_at_gmail.com>
Date: Mon, 25 Jun 2012 18:32:35 -0700
Subject: Re: Sizing Redo log files
On Wed, Jun 20, 2012 at 10:48 PM, Prasad Reddy Subbella <
Prasad_Subbella_at_infosys.com> wrote:
> Hi All,
> Please share/guide me the best practices to be used for sizing redo log
> files.
>
>
> Here's one:
Make sure that the time required to cycle through all (N-1) redo files is less than the time it takes to have the archivelogs created for (N-1) redo logs.
This should ensure that the archiver will not bump into the redo.
(please correct math if wrong, I am tired)
Jared Still
Certifiable Oracle DBA and Part Time Perl Evangelist
Oracle Blog: http://jkstill.blogspot.com
Home Page: http://jaredstill.com
-- -- http://www.freelists.org/webpage/oracle-lReceived on Tue Jun 26 2012 - 23:09:14 CDT