Re: CR Block copies, always 6 in

From: 조동욱 <>
Date: Tue, 25 Mar 2008 10:16:42 +0900
Message-ID: <>

> "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*"

It's a bit vague that i can't 100% understand what the author is trying to say.
Seems that he is referring buffer busy waits wait event but the timeout of buffer busy wait is 1s(100cs) not 10cs.
Asking it to the author seems to be good solution.

Jonathan Lewis has stated a quite probable answers to this situtation. My additional guesswork is that Oracle generates more CR blocks than the number limited by _db_block_max_cr_dba
when light work rule is applied on RAC system. But I don't have access to RAC at the moment that can't verify it.

Dion Cho

Received on Mon Mar 24 2008 - 20:16:42 CDT

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