RE: Materialized views and redo

From: Paul Vincent <Paul.Vincent_at_uce.ac.uk>
Date: Thu, 14 Jun 2007 10:02:15 +0100
Message-ID: <2AA2551968D1D349909FB594CC6310A27EA4@STAFFEXA.staff.uce.ac.uk>

Refresh type is FORCE, refresh mode is PERIODIC. There are 3 indexes on the MV, but setting them unusable before the refresh and rebuilding after the refresh would be impractical, since this is an hourly refresh.  

Paul Vincent
Database Administrator
Information and Communication Technology UCE Birmingham
paul.vincent_at_uce.ac.uk  

---

	From: Ajeet Ojha [mailto:ajeeto_at_gmail.com] 
	Sent: 14 June 2007 09:53
	To: Paul.Vincent_at_uce.ac.uk
	Cc: Oracle-L_at_freelists.org
	Subject: Re: Materialized views and redo
	
	
	if refresh type is complete then - 
	 
	oracle - first truncate the mv and then kind of does insert /*+
APPEND */ into the mv.
	so the redo will not be generated for table data but redo will
be generated for indexes.
	one way to minimize it - set the indexes unsuable and then

rebuild them after the refresh - now this is assuming that refresh type is complete and there are indexes on the mv in question.          

-Ajeet
-Oracle DBA
                  

        On 6/14/07, Paul Vincent <Paul.Vincent_at_uce.ac.uk> wrote:

                On a system which otherwise generates very little redo (since about 99% of all transactions are read-only, using only SELECTs), we have a materialized view which is refreshed once an hour. This was introduced to give a far better response time on a common query type which ran in 15 seconds without the view, but now runs in a second or less, using the materialized view.                  

                So far so good... but:                  

                Every time the materialized view is refreshed, this generates about 40Mb of redo activity, which means our archived logfiles area is now growing at a rate of around 1Gb per day. For comparison, before the materialized view was introduced, we only used to get about 50Mb of newly archived log files per day.                  

                Now, all this redo relates to the refreshing of an object which can easily be regenerated by simply refreshing the view. There's no conceivable scenario where this redo would ever be needed. So, is there any way of completely "switching off" the generation of redo log entries whenever the materialized view is auto-refreshed? This would save what's becoming a bit of a disk-space headache.                  

                Paul                  

		Paul Vincent
		Database Administrator
		Information and Communication Technology
		UCE Birmingham
		paul.vincent_at_uce.ac.uk 

		 

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Received on Thu Jun 14 2007 - 04:02:15 CDT