Re: data buffer access confusion
- From: Aman Sharma <amansharma1981@xxxxxxxxx>
- To: "Dunbar, Norman (Capgemini)" <norman.dunbar.capgemini@xxxxxxxxxxxxxxxxxxxxxxxxx>
- Date: Mon, 23 Aug 2010 12:45:57 +0530
Very good morning Norman,
Thanks for the reply first of all! I asked this question because this came
up at two different places, one in a conversation with an oracle
professional and the 2nd, in a book which I have just purchased. Before
replying to the author, I wanted to be sure that I am not missing anything
but despite checking at various places, I didn't find any explanation for
this term that data buffers can be stored in the PGA. Yes, there is a change
from 10g(10.2 I guess) that the data buffers can be stored in the shared
pool but that's all what I at least know. I never heard/read that PGA can be
used for the same.
Thank you so much for the reply and clarification once again Norman!
Regards
Aman....
On Mon, Aug 23, 2010 at 12:30 PM, Dunbar, Norman (Capgemini) <
norman.dunbar.capgemini@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
> Morning Aman,
>
> >> Is it a correct thing to say that when the data buffer is
> >> being read from the disk, its first kept in the PGA and then
> >> later on, it would be copied from the PGA memory to the
> >> standard buffer cache?
> Not quite.
>
> >> If no, then its alright but if yes, why such behaviour is there?
> It isn't - unless of course Oracle changed things recently!
>
> <SNIP>
>
> >> If anyone can explain and
> >> clear this confusion, it would be just great!
> The disc buffer(s) are read from disc - assuming that they are not
> already in the buffer cache - and placed into the buffer cache directly.
> Your server process then returns the block or blocks you requested to
> your user process.
>
> Now, I have to say that the last time I dealt with this was way back at
> Oracle 8.0 (!!!) so I'm now looking forward to being (a) corrected and
> (b) educated by those who know better than me!
>
>
> Cheers,
> Norman.
>
>
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