Re: db_file_multiblock_read_count and 10g
- From: Greg Rahn <greg@xxxxxxxxxxxxxxxxxx>
- To: 조동욱 <ukja.dion@xxxxxxxxx>
- Date: Sun, 25 Jan 2009 16:38:01 -0800
On Sun, Jan 25, 2009 at 3:42 PM, 조동욱 <ukja.dion@xxxxxxxxx> wrote:
>>
>> IIRC _db_file_exec_read_count=8 and
>> _db_file_optimizer_read_count=((max I/O size)/DB_BLOCK_SIZE)), so
>> usually 1MB I/O size.
>
> I think you mean _db_file_optimizer_read_count=8 and
> _db_file_exec_read_count = ((max I/O size)/DB_BLOCK_SIZE)).
I did. Caught a bit of dyslexia for a moment.
> This is a reasonable assumption, but I'm not sure how Oracle determines the
> maximum I/O size. On my laptop, Oracle 10.2.0.1 and 11.1.0.6 show quite
> different _db_file_exec_read_count.
>
> In 10.2.0.1 : _db_file_exec_read_count = 5
> In 11.1.0.6 : _db_file_exec_read_count = 128
>
> It seems quite dependent on Oracle version, not just on OS and/or storage
> settings.
Going from memory and not looking at the code, I think the db cache
size and number of processes also influence it, and I don't recall if
this changed between releases or not.
I'll research this a bit more next week if I have free time.
--
Regards,
Greg Rahn
http://structureddata.org
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