Re: Informix, Sybase, Oracle or MS SQL server

In article <DqJ278.1J5_at_mv.mv.com> Paul Chen <pchen_at_cougar.mv.com> writes:
>tkyte_at_us.oracle.com (Thomas J Kyte) wrote:
>
>So, if he is correct, are we required to use filesystems to build
>Oracle 7.0 database on UNIX if we want hot backup? If so, will this
>causedata integrity problem? Again, from the same book, on page 18,
>Michael R. Ault said the following.
>
> "If you use normal UNIX file devices, there is no guarantee that
> all updates will be written to disk in a timely manner. This is
> due to the UNIX file buffers. If a system crash should occur
> between the time data leaves the Oracle buffers and transits
> through the UNIX buffers, data could be lost."
>
I cannot speak for any Oracle behavior.

However for normal Unix files, most (if not all) Unixes provide the O_SYNC flag to either open(2) or ioctl(2) which guarantees that control does not return to the caller until the data and any associated control data (inodes etc), has been physically written.

I know that Informix uses synchronous writes on normal Unix files within Online, so for issues other than speed, cooked files are as safe as raw devices.

Scott Received on Sun Apr 28 1996 - 00:00:00 CEST