One small addition - there used to be a bug when explicitly setting
db_file_multiblock_read_count = 0 didn't enable the "self-tuning MBR", but
ended up setting the MBRC value to 1 instead (that's no good). So, one had
to completely unset the parameter in spfile/init.or, for the auto-selected
MBRC to kick in.
MOS Note: Unable To Set Db_file_multiblock_read_count Parameter To Zero
(Doc ID 1153666.1)
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Tanel Poder
https://tanelpoder.com/events
On Sun, Jan 17, 2021 at 10:40 AM Frits Hoogland <frits.hoogland@xxxxxxxxx>
wrote:
I too agree with most previous replies.
At a certain point in time in the past, setting
db_file_multiblock_read_count to 0 would make it oracle controlled and
dynamic. However since it’s not documented what it takes into account and
how it responds to it, I never used this setting, dynamic settings are
unpredicatable especially if the whole mechanism is undocumented. I just
read the db_file_multiblock_read_count parameter description in the oracle
19 documentation, and any mentioning of it being dynamic is gone, rather it
says that the default value is ‘maximum I/O size that can be performed
efficiently’ that is a rather clumsy and non-descriptive formulation.
