ADSM-L

Re: Backing up open files under NT?

2000-08-14 16:21:43
Subject: Re: Backing up open files under NT?
From: Thomas Denier <Thomas.Denier AT MAIL.TJU DOT EDU>
Date: Mon, 14 Aug 2000 16:21:20 -0400
> I'm a fairly new ADSM admin with a Unix background, and the NT team has been
> insisting that ADSM doesn't backup
> open files, and that an add-on product is required to do so.  This seems
> quite odd to me, but perhaps they know something I don't.
>
> OTOH, perhaps they have confused open files for running databases.
>
> How does ADSM handle open files under NT?

Open files as such are not usually a problem with NT. ADSM will back them up
and check to see if they changed while being read by ADSM. If need be, ADSM
will retry the backup as many as four times in an attempt to get a version
that did not change while being read. This is the default behavior. It is
possible to configure ADSM for other behaviors.

NT provides a mechanism by which a program that opens a file can request
exclusive access to the file. Files opened in this way are a much more
difficult problem than files opened without exclusive access. ADSM really
cannot read the files.

In my experience, three classes of files are commonly opened with exclusive
access. The first is the files making up the registry. ADSM has a built-in
circumvention for its inability to read these files. It uses an NT API to
query the registry contents, writes files containing the same key/value pairs,
and backs up those files.

The second class is user profiles for users logged on when the ADSM backup is
run. The NT administrators at my site regard this as a minor issue. In most
cases where profiles are not backed up ADSM already has a backup that was up
to date about 24 hours earlier. There are a few users who appear to never log
off. They could end up with a much older version of their profiles or even the
system default profile if we ever had to do a restore of user profiles.

The third class is database files. As far as I know, there are three ways to
handle these:
1.Shut the database down before the backup and restart it after the backup.
2.Buy an add-on product that uses database facilities to extract the database
contents and send them to ADSM.
3.Use facilities of the database product to export the contents to flat files
and have ADSM back up the flat files.
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