Try http://www.speakeasy.org/~jwilton/oracle/hot-backup.html for a view on this
John
-----Original Message-----
From: adary_at_mehish.co.il [mailto:adary_at_mehish.co.il]
Sent: 28 January 2002 09:20
To: Multiple recipients of list ORACLE-L
Subject: RE: COPY vs. OCOPY on NT
I seem to miss something here.
We are talking about backups that run after: alter tablespace XXX begin
backup.
There are no writes to the tablespace in this situation.
Yechiel Adar, Mehish Computer Services
adary_at_mehish.co.il
> -----Original Message-----
> From: Thomas B. Cox [SMTP:tbcox23_at_yahoo.com]
> Sent: Mon, January 28, 2002 6:35 AM
> To: Multiple recipients of list ORACLE-L
> Subject: COPY vs. OCOPY on NT
>
>
> Your point is (I believe) that the Oracle data files are
> opened writeable by Oracle at instance startup time. When
> you use the NT command "COPY" it will prevent additional
> writers, but not those writers that are already holding
> write locks.
>
> My comments and questions are:
>
> 1. This used to fail with an error in previous versions
> of Oracle and NT that I've worked with.
>
> 2. I'd be curious if multiple DB writers could cause
> a problem with your setup.
>
> 3. If a COPY fails/dies holding its lock, can I re-start
> either the COPY of Oracle without rebooting or manually
> clearing the lock?
>
> 4. You have demonstrated that the statement "COPY will
> always fail" is false. But we're not yet at "COPY will
> always work" -- and that could be a problem.
>
> Cheers.
> -Tom
>
>
> --- Igor Neyman <ineyman_at_perceptron.com> wrote:
> > Now, from my other message to the list (don't know, if Eric forwarded
> > it to
> > you), it answers your questions about my experience recovering from
> > online
> > backup and why I don't like MetaLink Note explanation in regard to
> > advantages of "Ocopy" versus "Copy":
> >
> > <quote>
> > 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:
> > <inner_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.
> > </inner_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).
> > </quote>
> >
> > And yes, I agree about Oracle (un-)support.
> >
> > Igor Neyman, OCP DBA
> > ineyman_at_perceptron.com
> >
> >
> > ----- Original Message -----
> > From: "Thomas B. Cox" <tbcox23_at_yahoo.com>
> > To: <PierceED_at_csus.edu>
> > Cc: <ineyman_at_perceptron.com>
> > Sent: Friday, January 25, 2002 3:38 PM
> > Subject: Re: ORACLE-L Digest -- Volume 2002, Number 025
> >
> >
> > >
> > > Could one of you forward this to your list? I'm not a subscriber.
> > >
> > > Also, I'm very curious if Igor can recover from his COPY hot
> > > backups, and if so, whether Oracle Support might actually be
> > > wrong.
> > >
> > > If nothing else, one might want to use OCOPY in order
> > > to get Oracle support in the case something goes wrong. I
> > > doubt they'd be able to help if one used an unsupported backup
> > > approach...
> > >
> > > Thanks.
> > > -Tom
> > >
> > > --- "Thomas B. Cox" <tbcox23_at_yahoo.com> wrote:
> > > >
> > > > I gave the right advice for the wrong reasons. My bad. I'll
> > revise
> > > > the next release of the paper and credit Igor -- thanks.
> > > >
> > > > Here's the word from Oracle Support:
> > > >
> > > >
> > > > Doc ID: Note:139327.1
> > > >
> > > > 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.
> >
> === message truncated ===
>
>
> =====
> Thomas B. Cox "Saepe in errore sed numquam in dubito"
> tbcox23@yahoo.com http://www.geocities.com/tbcox23/
>
> "The whole aim of practical politics is to keep the
> populace alarmed (and hence clamorous to be led to
> safety) by menacing it with an endless series of
> hobgoblins, all of them imaginary." --H.L. Mencken
>
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> Author: Thomas B. Cox
> INET: tbcox23_at_yahoo.com
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Received on Mon Jan 28 2002 - 09:45:36 CST
