Re: Rman - Curious Question
- From: "Joel Garry" <joel-garry@xxxxxxxx>
- Date: 28 Jul 2005 14:48:43 -0700
Holger Baer wrote:
> amerar@xxxxxxx wrote:
> > Hi All,
> >
> > Just a curious question:
> >
> > When you are duplicating a database which is on a differnt host, why
> > does it require you to copy the files to the remote host? Why can't
> > RMAN use the files on the primiary host?
> >
> > If you are using a recovery catalog, you use the catalog on the primary
> > host, so, why not also use the backup pieces? All the manual says is
> > that it requires you to copy the file.....
> >
>
> There is (at least) one misconception in your post: The catalog does only hold
> metainformation about the backups, so the fact that it is accessible
> is rather irrelevant for the question why the backup pieces ain't used.
> (In fact, it is recommended that the catalog and the target database are
> on different HW, so the files wouldn't be accessible through the catalog db).
>
> So the backup files are accessible primarily through the target
> - except if they are on tape and both machines can access the tape library
> - except if they are on a filesystem accessible to both machines.
>
> Why does Oracle not use Net 8? Because RMAN creates a server process on the
> target db and no-one in their right minds would like the production server
> to flood his network interface with the 1 TB you mention later in this
> thread.
This part I don't get. What is the difference between flooding the
interface with Net8, flooding it with ftp or flooding it with nfs?
It's still a T of data plus overhead, and you don't want to fight the
phone system over bandwidth for it.
I find the NFS method Sybrand quoted odd, as I think any NFS data
connection is suspect unless the hardware and software is specifically
OK'd by Oracle, so a flat "you can do it this way" would be wrong.
I'm sure at least part of the disagreement among the docs has to do
with the range of NFS implementations. Certainly any that are UDP
based wouldn't reliably work (guess what the U stands for - OK, it
stands for User, not Unreliable, although
http://www.faqs.org/rfcs/rfc768.html says "delivery and duplicate
protection are not guaranteed" ). And some modern NFS still are UDP
(for example, hp-ux 11i by default trys TCP first, then falls back to
UDP on failure). I've even seen rcp have problems with files over,
say, 20G (on a fast local network).
>
> I hope this clears the smoke
The fan seems to be making more smoke :-)
jg
--
@home.com is bogus.
http://www.signonsandiego.com/uniontrib/20050727/news_m1m27tfdmar.html
.
- References:
- Rman - Curious Question
- From: amerar
- Re: Rman - Curious Question
- From: Holger Baer
- Rman - Curious Question
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