Re: DWBR and dirty buffers

From: Jonathan Lewis <jonathan_at_jlcomp.demon.co.uk>
Date: Fri, 25 Feb 2005 07:03:14 +0000 (UTC)
Message-ID: <cvmiji$c84$1@hercules.btinternet.com>

The exacts details could change with
the size of the cache buffer - for reasons of side effects, not deliberate coding - a very small cache could results in a
different pattern of delay block cleanout, a very large cache could result in a
different availability of space for cloning blocks.

Don't forget to allow time for the checkpoints to complete, otherwise blocks that are due to be written for the checkpoint still be reported as dirty.

Could you clarify the line:
> After second checkpoint all "xcur" are flushed except one, which is "cr".

Blocks are not really 'flushed' by a checkpoint, only cleaned. So, in theory, you should see all the XCUR stay in memory and turn to CR

You may find that a few blocks seem to stay as xcur - check the objd (data object id) for these, it will probably be about 4 billion - meaning it's from a rollback segment. There's always a little background activity going on which means that a few more blocks will be dirtied even as the checkpoint is running.

-- 
Regards

Jonathan Lewis

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"Radoslav Rusinov" <radoslav.rusinov_at_gmail.com> wrote in message 
news:58aa0927.0502242240.6e2f6881_at_posting.google.com...


> According to last post from mr. Lewis

> I reissue my tests again and the remaining dirty blocks are not "cr".

> After first checkpoint the status of remaining dirty blocks is "xcur"

> (held exclusive by this instance).

> After isssuing of UPDATE all of dirty blocks are "xcur" (only one is

> "cr").

> After second checkpoint all "xcur" are flushed except one, which is

> "cr".

> Yesterday all of them was flushed and result was zero.

> Can someone try to explain what exactly is happened because this is

> not the same case like the previous one described by

> "wagen123_at_yahoo.com" and there are some

> misconceptions.

> Where exactly I am get wrong in my suggestions.

>

> Regards,

> Radoslav

Received on Fri Feb 25 2005 - 01:03:14 CST