Re: Upgrade to big SUN box or RAC for data warehouse?

Quarkman <quarkman_at_myrealbox.com> wrote in message news:<oprsqa790tr9lm4d_at_haydn>...
> On Tue, 22 Jul 2003 15:01:10 -0400, Ryan <rgaffuri_at_cox.net> wrote:
>
> > why would implementing RAC increase I/O? is that because of the 2 phase
> > commit? So you have to write to multiple datafiles?
>
> No.
>
> It may increase I/O for a number of reasons. A buffer in Instance A may
> have to be flushed for no other reason than Instance B has a past image of
> that buffer, and *it* needs to over-write its contents. The problem of
> forced disk writes (one instance making another instance do some I/O it
> wouldn't necessarily want to do on its own) has not been abolished in RAC
> (but it's better than it was in OPS).
>
> Secondly, the interconnect is not of infinite bandwidth, therefore
> reserving it for the transport of buffers which really, really need to be
> shipped to other instances in the shortest possible time may be quite
> important. Therefore, you use GC_FILES_TO_LOCKS to switch off cache fusion

   Can you elaborate on this please for those of us that have only experienced RAC as spectators? Can you provide some meaningful examples?

[deletia] Received on Wed Jul 23 2003 - 13:28:05 CDT