Re: RAID strip size and db_file_multiblock_read_count

Chuck,

1. Yes, you want to maximise the sequential reads, rather than incurr the performance penalty by moving the heads.
2. Sorry I don't follow your logic. You imply that it is better to perform more physical reads for one logical read, than have one physical read for one logical read.

As regards table scans, I would try to get the disk subsystem to do as many sequential reads as possible (fastest), couple that with tablespace and partition striping and the PQO.

Chris.

chuckh_at_safeplace.net wrote:
>
> The ORACLE tuning guide says that the minimum strip size to use in a raid
> array is twice that of db_block_size * db_file_multiblock_read count? Why is
> this? Won't that force each read for a table scan to be limited to one disk
> in the array? I'd think that you'd get better performance by making it just
> the opposite and so that each table scan read is done accross multiple disks.
> -- Chuck Hamilton chuckh_at_safeplace.net
>
> If at first you don't succeed, skydiving isn't for you!
>
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Received on Mon Mar 29 1999 - 16:12:31 CST