Re: CR Block copies, always 6 in

From: amonte <>
Date: Mon, 24 Mar 2008 12:56:45 +0100
Message-ID: <>

ok so the 6 doesnt seem the limit, I just check a 2 node RAC database ( on Solaris and shows this:

select file#, block#, status, count(*)
from v$bh
group by file#, block#, status
having count(*) > 6
order by 1,2, 4

returns 115 rows where some blocks has as large as 18 CR copies so the theory stated by the book doesnt seem real...


On Mon, Mar 24, 2008 at 12:15 PM, 조동욱 <> wrote:

> I read from somewhere, I think the wait interface book where it states
> that the number of clone copies of data block is governed by
> _DB_BLOCK_MAX_CR_DBA which is set to 6. If there will be more than 6 copies
> then Oracle will wait for the buffer, this is what I dont get, wait?
> Can you point us to the original doc?
> I've never heard that consistent read is blocked and being waited by any
> reason.
> (One exception is that buffer lock contention which is caused by physical
> read - read by other session wait event)
> As you observed it right, cr blocks are recycled by age.
> The olest one is replaced by new cr block.
> You can verify it using x$bh view.
> Dion Cho
> PS)
> "I read somewhere..." kind of thing seems not to be a good habit.
> You'd better leave a link to original doc or make the replayable test case
> yourself.

Received on Mon Mar 24 2008 - 06:56:45 CDT

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