RE: I/O and db_file_multiblock_read_count

We also use Hitachi Sans. I ran dd for 64K and 1M block sizes and the reads with 1M block size were slightly faster. This is on Solaris8 / Sunfire 15K.

Strangely, the sys time is much lower with the 1M blocksize. Is there an explanation for that?

Keith

orapls> time dd if=polaris_data_04.dbf of=/dev/null bs=65536 163840+1 records in
163840+1 records out

real 4m15.57s
user 0m0.85s
sys 2m37.34s
ddcspora07 - pol2p - /plsoraprd01/u03/oradata/pol2p

orapls> time dd if=polaris_data_04.dbf of=/dev/null bs=1048576 10240+1 records in
10240+1 records out

real 3m59.18s
user 0m0.02s
sys 0m21.93s

> do the "same" thing using dd. Whatever your db_block_size is, plug it in
> as follows:
>
> $ time dd if=<datafile_for_the tablespace> of=-/dev/null
> bs=<block_size_in_bytes*16>
>
> then re-run:
> $ time dd if=<datafile_for_the tablespace> of=-/dev/null
> bs=<block_size_in_bytes*128>
>
> please let me know what you find
>
>
>
>
> ________________________________
>
> From: oracle-l-bounce_at_freelists.org
> [mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Kevin Lidh
> Sent: Friday, December 08, 2006 12:46 PM
> To: oracle-l
> Subject: I/O and db_file_multiblock_read_count
>
>
> I was reading an article about the appropriate setting for
> db_file_multiblock_read_count. I'm on a HP-UX 11.11 64-bit system with
> Oracle 9.2.0.7.0. The original value was 16 and I bounced the database
> and ran a million record full-scan test (10046 trace) and then set the
> value to 128 (max value) and re-ran the
>
>

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