Re: Raw Devices: Increased Performance?

Joel Garry wrote:
>
> An unintended side effect is, poorly optimized apps that force too
> many full-table scans will do better with raw devs...
>

I would have said that there is an opposing argument to that.

If you do tablescans in Oracle, the data blocks are not kept in the SGA, so a repeated tablescan does the same set of disk reads agsin.

With a file system, the disk reads may be satisfied from the file system buffer. With raw devices they will be physical reads. Result: a bad app collapses when moved to raw disk.

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Jonathan Lewis
ora_mail_at_jlcomp.demon.co.uk