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Hi,

a couple of things got confused. I try to clarify:

a)
- ON-Bar does support parallel backups and restores.
The onconfig file parameter to configure this is BAR_MAX_BACKUP .
- having set BAR_MAX_BACKUP to 1 will in fact make ON-Bar
operate serially.
- recommended setting of BAR_MAX_BACKUP is # of parallel
operations that the storage manager can handle minus 1.
The minus 1 is to keep some resources free for logical log
backup (which may be triggered any time when a log becomes full).
- ON-Bar does parallelize backup and restore operation based on
dbspaces, because dbspaces are the backup objects (viewpoint
from the storage manager side). The parallelism is not determined
by the number of chunks. If you have 1 dbspace (rootdbs) with
100 chunks, then you will not see any parallelism.
- setting BAR_MAX_BACKUP to 0 (zero) will parallelize as much as
possible. This depends on the number of dbspaces you have.
Critical dbspaces (especially rootdbs) are handled first, everything
else in parallel. So with this setting and having 100 non-critical
dbspaces, ON-Bar will start 100 dbspace backup processes in
parallel. Each of these processes will backup all chunks (serially)
that belong to the individual dbspace the process is working on.

b)
- IBM does not provide an "XBSA agent for 3rd party backup vendors".
I'm not even sure what is meant by this term.
- ON-Bar always works with a storage manager. Without storage
manager you can't use ON-Bar. The communication between
ON-Bar and the storage manager is via a shared library that implements
the XBSA (X/Open Backup Services API).
This shared library is always part of the storage manager product.
It is not part of ON-Bar. ON-Bar only uses it.
- a storage manager can be implemented in a client-server architecture.
In that case the client runs on the same machine as ON-Bar (and IDS)
and the storage manager server can run on a remote machine.
However, this does not change how ON-Bar uses the XBSA shared
library and this shared library is still a part of the storage manager
client.

c)
- since ON-Bar cannot be used without a storage manager, IBM is
packaging a slimmed down storage manager with the IDS product.
This storage manager is called ISM (Informix Storage Manager) and
is actually derived from Legato's storage manager.
- this ISM has its own XBSA shared library (no surprise here).
- Being free (no additional charge) ISM is not a full-blown storage
manager.
Therefore it has some limitations, the most important are:
- ISM does not work via network, i.e. in general the storage manager
has to run on the same machine as ON-Bar (and IDS).
- ISM can support only up to 4 devices in parallel. Therefore when
using ISM, the recommended setting for BAR_MAX_BACKUP is 3
(keeping one device resource free for logical log backup).

d)
Who is this vendor that said such things ?

Regards,
Martin
--
Martin Fuerderer
IBM Informix Development Munich, Germany
Information Management

owner-informix-list@iiug.org wrote on 07.03.2005 02:11:17:
> Hi All,
>
> I have a question for you regarding onbar and backups. I was under the
> impression that onbar supported parallel backups/restores to/from
multiple
> drives. Does the XBSA agent provided by informix for 3rd party backup
> vendors also support parallel backups/restores
>
> I have looked in the backup restore manual and there is no mention of
not
> supporting this but apparently the vendor has said that it is an
inherent
> limitation of informix. I wanted to be sure of my facts before replying.
>
> Any clarification would be much appreciated.
>
> Regards
> Stefan
> sending to informix-list

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