Re: Buffer use under Oracle

From: K Gopalakrishnan <kaygopal_at_yahoo.com>
Date: Wed, 12 May 2004 21:16:55 +0530
Message-ID: <007401c43838$5d0f3be0$0200010a@idc.oracle.com>

Cary:

I don't think this is right unless I am reading between lines ;). Cloned buffers are always kept in the cold end in the new alogorithm and they are ready to be flushed when ever there is a demand for new buffers. The CR buffers are kept in the FROZEN end (note the word freeze in the parameter, it is not cold. Freeze)

Of course the behavior can be controlled by _db_aging_freeze_cr parameter.

> >Why aren't the old ones freed when a new one is created?
>
> ...because of Oracle's LRU buffer cache management algorithm.
> Currently-executing queries may "like" having a slightly older CR copy =
> of a
> newly modified block in the buffer cache. Such a block will tend to =
> remain
> cached as long as some session keeps using it. Those blocks are in your
> buffer cache because your application needs them.
>

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Received on Wed May 12 2004 - 11:24:54 CDT