Re: CR Block copies, always 6 in

From: amonte <>
Date: Mon, 24 Mar 2008 12:52:20 +0100
Message-ID: <>

Do you have the wait interface ebook?

Its in page 221 where it says:

"To avoid flooding the buffer cache with cloned buffers, Oracle limits the number of cloned buffers (or cr copies) to six per data block address . Once the limit is reached, *Oracle waits for the buffer; the normal wait time is 10cs before it attempts to clone/reread the buffer*"

TIA Alex

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 - 06:52:20 CDT

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