Re: 8.1.7 cache buffer chains contention

comments below..

"Jonathan Lewis" <jonathan_at_jlcomp.demon.co.uk> wrote in <998981715.4981.0.nnrp-13.9e984b29_at_news.demon.co.uk>:

>I've had a couple of thoughts about your latching
>problem, and changes to the way Oracle may be
>working.
>
>1st thought is the index root block that you've identified
>also an index leaf block ? If so, then Oracle may pin the
>block whilst scanning the the table blocks - but this
>is a recent change to the code. It may be that the
>action of pinning and unpinning the block takes an
>amount of time proportional to the number of processes
>currently on the pin-list - and in your case you have lots
>of concurrent processes.
>

No its not a leaf block as well.

>2nd thought - how many versions of the block appear
>on the hash-chain ? There is supposed to be a limit
>of 5 or 6. If there are too many, then the time taken
>holding the latch whilst scanning for the correct
>version of the buffer will go up. On the other hand, if
>there are too few then the concurrent processes may
>keep on flushing each other's CR images and having
>to rebuild them thus increasing the number of times
>buffers have to be pinned for copying.
>

I just checked to see how many versions of that block showed up in X$bh, and there was only one.
>
>--
>Jonathan Lewis
>
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Received on Tue Aug 28 2001 - 10:10:44 CDT