Re: 9i multi cache buffer

The old biblical one about 'motes and beams' (King James version - possibly 'sawdust and planks' in more modern versions) springs to mind.

Whilst Oracle publishes tpc's that appear to get performance benefit from multiple block sizes I think most users will take the (wrong) hint and depend on the feature for performance benefits - whilst failing to notice other, far more significant, options for performance improvement.

Here's a thought for performance, though. If you have a 2K block size for UNDO on
an OLTP system - every undo block is likely to waste about 400 bytes i.e. 20%. If you change to 16K blocks, that's only 2.5%,
which means more efficient use of buffer space - hence less I/O, hence ... Of course, I can come up with three reasons why this apparent performance enhancer will lead to worse performance - dependent on the exact nature of your application and installation !

Remember the Xerox salesman's cry:

    "Sell benefits, not features"

--
Regards

Jonathan Lewis
http://www.jlcomp.demon.co.uk

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Mark Townsend wrote in message ...


>

>The reality is that for most workloads (and I'd dare to say all

customer


>workloads), the performance benefits from multiple block sizes will

not make


>a significant impact, and in fact, I doubt would be measurable at

all.


>

>Hopefully this will close this thread (as it did the one that went

through


>Oracle about 6 months ago on this same topic)

>