Re: OS Block Size - MS Windows NT

In article <8b7vo0$1i7$1_at_zrtph05m.us.nortel.com>, "Sisk, David [YRK:6J00:EXCH]" <dsisk_at_americasm01.nt.com> wrote:
> Actually, one statement is not correct. Oracle does not bypass NT's
> caching. Oracle writes are cached just like any other writes on NT
 unless
> you are writing to raw disk partitions. This is why OPS on NT has to
 be run
> on raw disk (just like on unix).
>
> Regards,
> D.
>
>

Well...for what it's worth (and I wonder what) here are two quotes from Oracle support:

"Oracle uses non-buffered reads and writes on NT. We therefore bypass the NT file system cache and are thus only concerned with I/O in multiples of the O/S blocksize (512 bytes)...So if we want to read a 2k Oracle block we pass this to the O/S who simply does a 2k read (4 sectors) from the existing file and passes the results back to Oracle and our own buffer cache."

"Oracle does a bypass of NT buffer cache, this is done because the API win32 provides a flag called FILE_FLAG_NO_BUFFERING , that is used by Oracle when the datafiles are created. Also, you can confirm this doing a simple full scan on a large table, several times, and you can observe that the response time will be the same"

The mystery continues (?)

--
Ben Pomicter
Database Administrator
Digitas


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