Re: OS timestamps during hot backup

From: Jeremiah Wilton <jeremiah_at_wolfenet.com>
Date: Tue, 13 Apr 1999 08:42:54 -0700
Message-ID: <Pine.OSF.4.02.9904130824000.1694-100000@gonzo.wolfenet.com>

On Mon, 12 Apr 1999, David Lai wrote:
>
> Oracle datafiles' OS timestamps are usually not updated until
> the database is shutdown. It seems logical to me that when a
> tablespace is put in hot backup mode the OS timestamps of its
> datafiles should be updated (for OS level incremental backups).
> I was running Oracle 8.0.5 on HP-UX 11.0 and when I put the
> database in hot backup mode I did not notice any changes in
> the OS timestamps of the datafiles. Could someone tell me why?

Oracle does not close the datafile while in hot backup mode. Oracle continues to write to the files as it always does. The only differences between hot backup mode and normal operation are:

The CHECKPOINT SCN value in the file header is not updated.
The HOT BACKUP CHECKPOINT SCN value in the file header is updated.
For the FIRST CHANGE while in backup mode of any particular block in the file, the full image of that block is logged to the redologs.

So, there is no reason that the MTIME per the O/S should appear any different for datafiles in backup mode.

--
Jeremiah Wilton http://www.wolfenet.com/~jeremiah Received on Tue Apr 13 1999 - 10:42:54 CDT