IDS Forum

RE: regarding restore using ontape

Posted By:
Date:

Hi,

if I understand the (original) question correctly, then you are
trying to restore a dbspace from one system into another system,
but you want to leave the rest of this other system as it is.

Hmm. This is very tricky.

You can do a restore of a single dbspace, and it can even be
a warm restore (as long as that dbspace is not a critical dbspace).
However, to avoid inconsistencies, the restored dbspace needs to
be brought to the same state as the other dbspaces. This is done
by applying logical log records to the restored dbspace. Nothing tricky
sofar.

Now in your case, you restore the dbspace from an archive taken on
a different system. The physical restore probably works fine - after
all it just copies (data) pages from the archive to disk(s).
But after that the dbspace is not consistent with the rest of the
system. To bring it to consistency, the logical restore part now needs
to be performed. This is when the logical log records will be
applied to the physically restored dbspace.

In your case the question at this point is, which logical log records
should
be applied to the restored dbspace ? Log records from the different
system, i.e. the one where the dbspace was backed up ? Or log records
from the system where the dbspace was restored ?
Either way - I would not expect this to work properly and give you
a restored dbspace that is consistent with the rest of the system.
I think you are bound to run into trouble somewhere. Worst case is,
coincidently the restore worked, but you have logical inconsistencies
that cannot be detected by the system/restore. Only you will have faulty
data in your database and get wrong results upon queries ...

Having said that - I would not (try to) do it.
Besides, I have not heard that it would be supported.

Restoring a table only from an archive is a much requested feature.
It has not been implemented sofar, so it's not available in 9.40.UC1.

It might be added in a future release ... :)

Regards,
Martin
--
Martin Fuerderer
IBM Informix Development Munich
Data Management Solutions





"ART KAGEL, ...." <KAGEL@bloomberg.net>
Sent by: forum.subscriber@iiug.org
11.03.2003 15:25


To: ids@iiug.org
cc:
Subject: RE: regarding restore using ontape [643]




IN order to restore the number of chunks and the chunk paths must be
identical
and the physical size of each chunk must be AT LEAST as large as on the
system
where the archive was made, including the root chunk. The dbspace and
chunk
information stored in the local instance are IGNORED at the time of the
restore
as the reserved pages are restored from the archive essentially wiping out
the
local instance and replacing it with an image of the source instance. If
all of
the chunks recorded on the tape do not exist or are not large enough the
restore will abort without writing anything.

Art S. Kagel

----- Original Message -----
From: Nagarjuna Kurra <nagarjuna.kurra@gujaratgas.com>
At: 3/11 9:10

> hi
>
> thankyou very much , is it possibe to restore the backup of one
system
> on other system ( ontape backup 0 level) where the no of chunks, sizes
of
> rootdb space, logdbspace and phydbspace are different but the dbspaces
which
> i want to restore has same no chunks and same chunk sizes. is that
psssible
> to restore uning ontape -r -d dbs2 .
>
>
> is there any posiibility to read ontape archive tape and restore single
> table (either using unix utilites).i am using IDS 7.30UC7A on HP unix
10.2.
>
> with regards
>
> nagarjuna.K

Messages In This Thread

• RE: regarding restore using ontape
  ART KAGEL, BLOOMBERG/ 65E 55TH -- Tuesday, 11 March 2003, at 9:25 a.m.
  • RE: regarding restore using ontape
    Martin Fuerderer -- Tuesday, 11 March 2003, at 11:02 a.m.

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