RE: db_file_multiblock_read_count and performance

Hi Ryan
>I have been testing this extensively over the last few months. I do a full table scan with a
>db_file_multiblock_read_count = 1 and then one = 128( i check the 10046 trace to verify i am
>getting this much) and I see absolutely no difference whatsoever in response time.

Attached you find some results that I get during some tests that I performed on different servers by different customers (notice that I had no influence on the setup, I just run a test script...).

As you can see many different behaviors are to be expected.

System 1: higher values are better, of course they are "technical" limits... (notice that 55MB/s is the maximum throughput measured on this system, i.e. with DFMRC=32).

System 2: values higher than 16 give bad performance, i.e. the optimal value is 16.

System 3: values less than 17 are useless, i.e. at least 17 should be used to have "correct" performance.

System 4: no performance difference was measured. Notice that this system, with 230MB/s, is also the faster I tested...

HTH
Chris

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