RE: COPY vs. OCOPY on NT

Taking back my comment.
Standing corrected.
Eating humble pie
ETC.... Tom Mercadante pointed me to a very clear paper that explains oracle behavior during backup.
http://www.backupcentral.com/oracle-hot-backup.html

Thanks Tom and Jared.

Yechiel Adar, Mehish Computer Services
adary_at_mehish.co.il

> -----Original Message-----
> From: Jared Still [SMTP:jkstill_at_cybcon.com]
> Sent: Mon, January 28, 2002 3:41 PM
> To: Multiple recipients of list ORACLE-L
> Subject: Re: COPY vs. OCOPY on NT
>
>
> Oh boy, not that old chestnut again.
>
> You better take a close look at the concepts manual, as there
> are indeed writes to the data files making up the tablespace
> regardless of whether the tablespace is in backup mode or not.
>
> The details of what occurs during 'alter tablespace begin backup'
> are readily available at tahiti.oracle.com.
>
> You may also find some helpful information at www.orafaq.com
>
> Jared
>
>
> On Monday 28 January 2002 01:20, ????? ??? wrote:
> > 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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> Please see the official ORACLE-L FAQ: http://www.orafaq.com
> --
> Author: Jared Still
> INET: jkstill_at_cybcon.com
>
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