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Oracle _log_io_size parameter
By Burleson Consulting
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Redo log contention is a function of several
parameters and the size of
the log_buffer.
Steve
Adams notes the benefit of the hidden parm _log_io_size:
Most importantly, ensure that LGWR is
not overactive because of too low a _log_io_size setting, and
that DBWn is not checkpointing recently changed blocks too
intensively.
At the application level, beware of spurious COMMITs, avoid SELECT FOR UPDATE statements and before row
triggers, and code DML operations to minimize redo generation.
For example, you could set _log_io_size
to about 64k or so which typically is a _log_io_size of about
125 log blocks if the log block size is 512. This will have two
benefits....
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The log buffer can handle bigger
transactional loads
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It will stream out redo as it's generated
(typically Oracle is very lazy about this. Oracle will
only start writing redo out when the log buffer is about 1/3
full which means that when
it does write, it's a bursting type of write).
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