CR Block copies, always 6 in

From: amonte <>
Date: Mon, 24 Mar 2008 01:10:05 +0100
Message-ID: <>

Hi all

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?

So I fired up 7 sessions and see what kind of wait is this! I updated the same table (EMP from scott tiger), 14 rows in same data block and each session updates a row, then each session fires a query agaisnt EMP. I noticed that the number of CR is never more than 6 despite having 7 updates concurrently and I dont see what is really going on. Does this mean whenever the 7th CR block is being cloned one of 6 previous CR is being overwritten or "destroyed"?

I did the test in

TIA Alex

Received on Sun Mar 23 2008 - 19:10:05 CDT

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