Ok, I guess, I owe some explanation here, since I've got a lot of spanking
(replies, some rather sarcastic) regarding this issue.
My original note comes from my "real life" experience, so I'm still standing
behind it.
Sorry, it'll be kind of long, but if you are really interested...
Couple years ago, when we were preparing first release of our product, I
read of course about "NT Copy" versus "Oracle Ocopy".
Still I decided to test it, because not always I trust what I read, and I
like to get proof myself.
Testing of online ("hot") backup/recovery scenario showed, that using "NT
Copy" command in backup scripts is perfectly fine, when creating backup set
of files on the disk. And there is no problem restoring from this backup.
Now this "disk backup" set of files could be saved on tape, using NTBACKUP
(that's the one, that really can not copy file, if it's opened by some other
program. But that's not the case with prepared in advance "disk backup").
"NT Copy" has no problems copying files opened already by Oracle, and backup
is consistent, as long of course as I am using "alter tablespace <name>
begin backup" before copying relevant files and "alter tablespace <name> end
backup" after finishing files copy.
So, those scripts (using "NT Copy") were put into production, and now have
been used for more than two years on more than hundred installations/sites
(the number keeps growing).
>From time to time, our field engineers are bringing back to me sets of
online (can not use "cold" backup - our systems should run 24*7, I'm not
saying they are, but we are trying to minimize downtime) backed up files (db
files and archived RedoLog files), and I recover them with no problem (we
need this, to test how the upgrade to next release of our product will run
against "real" customers data).
Now, about MetaLink Note:139327.1
It says:
<quote>
Ocopy opens the file using CreateFile() with the FILE_SHARE_READ and
FILE_SHARE_WRITE flags. This allows writing to continue while we take the
backup. Inconsistencies in the backup are repaired by applying archived
redo during recovery. The 'copy' command from NT doesn't use these flags
since it wants to prevent writes to the file while the copy is taking
place.
</quote>
I don't think, it's very accurate, and here is why:
When during online backup I run "NT copy" against db file, the file is
already opened by Oracle (at moment, when I "open" the database).
So, even if "NT copy" opens file without FILE_SHARE_READ and
FILE_SHARE_WRITE flags, all it means is that "Subsequent open operations on
the object will fail" (quote from NT docs). I want you to notice, it says
"Subsequent open operations" not "Subsequent write/read operations". So,
all it does is prohibiting some other program/process from "opening" the
file. But Oracle, as I mentioned, has this file already opened, and it is
perfectly capable of reading/writing this file.
Of course, the image of the saved file will be "fuzzy", and that's why when
recovering from online backup we are applying archived RedoLog files (which
getting written much more intensely during online backup).
As for Peter McLarty note, that he "never knew that NT copy could manage
keeping the CSN number in sync",
well it ("NT Copy") does not have to (neither does "Oracle Ocopy") keep CSN
number in sync.
Oracle updates file header with checkpoint SCN, when we issue "alter
tablespace <name> begin backup". Then until "alter tablespace <name> end
backup", file header will cease updating. And SCN, written in the beginning
provides the info, which archived RedoLog files should be used for recovery.
Now, please correct me, if I'm wrong.
Igor Neyman, OCP DBA
ineyman_at_perceptron.com
- Original Message -----
To: <ORACLE-L_at_fatcity.com>
Cc: <ineyman_at_perceptron.com>
Sent: Thursday, January 24, 2002 6:47 PM
> > Wrong. NT 'COPY' has no problems copying 'opened' oracle db files.
> > I'm using it in 'hot backup' scripts on many dozens systems, and it
> works
> > fine.
>
> Igor, you sure about that?
>
> There are backup packages (such as Backup Exec ) that use their
> own file open copy program to avoid using copy.exe.
>
> Have you restored any of these backups made with copy?
>
> Jared
>
> Note:139327.1
> Subject:
> Differences between Windows NT COPY and Oracle
> OCOPY When Doing Backups
>
> Creation Date: 03-APR-2001
> Last Revision Date: 04-DEC-2001
>
> PURPOSE
> A comparison of the differences between the Windows NT "copy" commnad,
> and
> the Oracle "ocopy" command. Which should be used during an online
> backup?
>
> SCOPE & APPLICATION
> DBAs with databases on the Windows NT platform.
>
> The Differences between Windows NT COPY and Oracle OCOPY When Doing
> Backups:
>
>
>
> When doing an online backup, should you use the Windows NT COPY command,
> or the
> Oracle OCOPY command?
>
> While doing online backups you should use OCOPY, or Oracle7 EBU, or
> Oracle8
> (and later) RMAN. With the OCOPY command you could copy to a backup
> directory
> on the hard drive but cannot use OCOPY to copy a file to tape. The other
> option
> if you do not want to use ocopy to perform your backup as this does
> require a
> lot of disk space is EBU/RMAN that comes with Oracle. Depending on your
> Oracle
> version, the distribution includes a utility called EBU (Oracle7) or RMAN
>
> (Oracle8 and later) that can be used for online recovery as well. You
> will need
> to use a media management product to move the data from RMAN to tape.
> Legato
> Storage Manager is provided however there are other products that are
> supported
> to be used with this tool.
>
> To backup you will need to use the utility delivered by Oracle, the ocopy
>
> command. Utilities like the NT commands copy, xcopy CANNOT be used to
> back up.
> The Windows NT feature to be aware of is that NT Backup does not allow
> files in
> use to be copied, so you must use the OCOPY utility that Oracle provides
> to
> copy the open database files to another disk location. Since OCOPY cannot
> copy
> files directly to tape, you will then need to use NT Backup or copy or a
> similar utility to copy the files to tape, as required.
>
> OCOPY allows writing to continue while the backup is running. The NT COPY
> is a
> closed copy and the files may be marked either as "fuzzy" or "corrupt."
> Ocopy
> opens the file using CreateFile() with the FILE_SHARE_READ and
> FILE_SHARE_WRITE
> flags. This allows writing to continue while we take the backup.
> Inconsistencies in the backup are repaired by applying archived redo
> during
> recovery. The 'copy' command from NT doesn't use these flags since it
> wants to
> prevent writes to the file while the copy is taking place.
>
>
>
>
>
>
> "Igor Neyman" <ineyman_at_perceptron.com>
> Sent by: root_at_fatcity.com
> 01/24/02 01:05 PM
> Please respond to ORACLE-L
>
>
> To: Multiple recipients of list ORACLE-L
<ORACLE-L_at_fatcity.com>
> cc:
> Subject: Re: Backup Strategy
>
>
> I took a quick look at this paper, and found right away, that it's not
> very
> accurate, at least in one issue.
> i.e., it states :
> < quote>
> The Windows NT command COPY can be used to create a cold backup of a
> database. It cannot be used to make a
> hot backup. Attempting to perform a hot backup with COPY will usually
> result
> in an error message being generated
> as the COPY command fails - during a hot backup the database is running
> and
> thus the database files are locked by
> the Oracle database process, and COPY cannot work on a file that is so
> locked.
> < /quote>
>
> Wrong. NT 'COPY' has no problems copying 'opened' oracle db files.
> I'm using it in 'hot backup' scripts on many dozens systems, and it works
> fine.
>
> Don't know about the accuracy of the rest of the paper, didn't have time
> to
> read it all.
>
> Igor Neyman, OCP DBA
> ineyman_at_perceptron.com
>
>
> ----- Original Message -----
> To: "Multiple recipients of list ORACLE-L" <ORACLE-L_at_fatcity.com>
> Sent: Thursday, January 24, 2002 7:35 AM
>
>
> > Hi All,
> >
> > http://www.geocities.com/tbcox23/
> >
> > Go here and get the paper.
> >
> > Regards
> > Venkat
> > --
> >
> > On Thu, 24 Jan 2002 03:25:17
> > Bunyamin K. Karadeniz wrote:
> > >If possible , I want one copy too.
> > >Bunyamin
> > >----- Original Message -----
> > >To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com>
> > >Sent: Thursday, January 24, 2002 12:30 PM
> > >
> > >
> > >> Can you send me one (NT backup strategy)
> > >>
> > >> Regards,
> > >> Ramesh D Papnoi
> > >> Oracle DBA @ Chemtex Global Engineers Pvt. Ltd., Mumbai, India
> > >> (BrainBench & Brainbuzz Certified Oracle 8/8i DBA & Developer)
> > >> http://www22.Brinkster.com/rpapnoi
> > >>
> > >> ---------- Original Text ----------
> > >>
> > >> To: internet["Multiple recipients of list ORACLE-L"
> > ><ORACLE-L_at_fatcity.com>]
> > >>
> > >> Please send me one. (NT) Thank,
> > >>
> > >> grace wrote:
> > >> >
> > >> > can u also send me a copy on backup strategy on nt.
> > >> > thanks
> > >> >
> > >> > ----- Original Message -----
> > >> > To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com>
> > >> > Sent: Wednesday, January 23, 2002 3:25 PM
> > >> >
> > >> > > Hello Hamid
> > >> > >
> > >> > > I would like to have this paper as well.
> > >> > > We are now revising our Backup strategy.
> > >> > >
> > >> > > Yechiel Adar, Mehish Computer Services
> > >> > > adary_at_mehish.co.il
> > >> > >
> > >> > > > -----Original Message-----
> > >> > > > From: Mohan, Ross [SMTP:MohanR_at_STARS-SMI.com]
> > >> > > > Sent: Tue, January 22, 2002 6:35 PM
> > >> > > > To: Multiple recipients of list ORACLE-L
> > >> > > > Subject: RE: Backup Strategy
> > >> > > >
> > >> > > > Hamid,
> > >> > > >
> > >> > > > Would you be willing to forward a copy of
> > >> > > > this paper?
> > >> > > >
> > >> > > > Thanks,
> > >> > > >
> > >> > > > Ross Mohan
> > >> > > >
> > >> > > > -----Original Message-----
> > >> > > > Sent: Thursday, January 17, 2002 12:27 PM
> > >> > > > To: Multiple recipients of list ORACLE-L
> > >> > > >
> > >> > > >
> > >> > > > Hi List,
> > >> > > > I have a white paper for Backup Strategy on Microsoft NT but I
> am
> > >> > looking
> > >> > > > for Backup Strategy for Oracle8i on Solaris, If anybody have
> any
> doc
> > >or
> > >> > > > link
> > >> > > > I realy appreciate.
> > >> > > >
> > >> > > >
> > >> > > >
> > >> > > >
> > >> > > > Hamid Alavi
> > >> > > > Office 818 737-0526
> > >> > > > Cell 818 402-1987
> > >> > > >
> > >> > > > The information contained in this message and any attachments
> is
> > >> > intended
> > >> > > > only for the use of the individual or entity to which it is
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> > >> > and
> > >> > > > may contain information that is PRIVILEGED, CONFIDENTIAL and
> exempt
> > >from
> > >> > > > disclosure under applicable law. If you have received this
> message
> > >in
> > >> > > > error,
> > >> > > > you are prohibited from copying, distributing, or using the
> > >information.
> > >> > > > Please contact the sender immediately by return e-mail and
> delete
> > >the
> > >> > > > original message from your system.
> > >> > > > --
> > >> > > > Please see the official ORACLE-L FAQ: http://www.orafaq.com
> > >> > > > --
> > >> > > > Author: Hamid Alavi
> > >> > > > INET: hamid.alavi_at_quovadx.com
> > >> > > >
> > >> > > > Fat City Network Services -- (858) 538-5051 FAX: (858)
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> --
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> Author: Igor Neyman
> INET: ineyman_at_perceptron.com
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--
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Received on Fri Jan 25 2002 - 10:37:07 CST
