The argument for direct io is that if you already have
a large cache (the oracle one), then its not much use
having a second copy of that cache (the unix one) -
that memory could possibly be better used elsewhere
(supporting more users, large sort sizes etc etc etc)
So having direct io is giving more of the caching
responsibility to the oracle buffer cache.
hth
connor
--- KC <[EMAIL PROTECTED]> wrote: > Dear list,
>
> Our shop is running Solaris 2.6, Oracle database
> 8.0.6 and Veritas VxFS file system. At present, all
> database file access thru the file system buffer
> cache, we decided to use the direct I/O mount option
> with VxFS for performance reason. There is one issue
> I am not sure about and hope someone on the list can
> give me a pointer, access database file thu the file
> system buffer cache gives us "read ahead" advantage,
> with direct I/O I think what you read is what you
> get (no read ahead functionality), is this an
> issue?? If it is an issue, how do you deal with it??
> WIth file system buffer cache, I think the database
> block size should be the same as file system buffer
> size and file system block size is irrelevant to how
> much system read or write, is this still true under
> direct I/O, I am not sure what dictate how much data
> to read or write??
>
> KC
>
=====
Connor McDonald
http://www.oracledba.co.uk (mirrored at
http://www.oradba.freeserve.co.uk)
"Some days you're the pigeon, some days you're the statue"
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