Oracle FAQ Your Portal to the Oracle Knowledge Grid
HOME | ASK QUESTION | ADD INFO | SEARCH | E-MAIL US
 

Home -> Community -> Mailing Lists -> Oracle-L -> Re: I/O activity during HOT backups

Re: I/O activity during HOT backups

From: Vidya Kalyanaraman <kvidya13_at_hotmail.com>
Date: Wed, 21 Jun 2000 10:58:05 EDT
Message-Id: <10535.109999@fatcity.com>


Hi Ruth,
Here it goes again...
www.wolfenet.com/~jeremiah/hot-backup.html

Thanks
Vidya

From: "Ruth Gramolini" <rgramolini_at_tax.state.vt.us> Reply-To: ORACLE-L_at_fatcity.com
To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com> Subject: Re: I/O activity during HOT backups Date: Wed, 21 Jun 2000 06:58:11 -0800

Could you post the link again. I have been looking for it and I can't find it. Thanks!
Ruth
----- Original Message -----
To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com> Sent: Tuesday, June 20, 2000 11:07 AM

> William,
> That book you are refering has erroneous descriptions of hot backup.
> Pls read this article by Jeremiah...I have already posted this link to
> list....
> This article talks mainly about "Oracle Unleashed...." book and its
> misleading hot backup concepts.
> Thanks
> Vidya
>
>
>
> Reply-To: ORACLE-L_at_fatcity.com
> To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com>
> Date: Tue, 20 Jun 2000 05:57:30 -0800
>
> The following is a quote from my favorite Oracle reference boot titled
> "Oracle Unleashed, Edition 2" by SAMS Publishing.
>
> When you place a tablespace in backup mode, the Oracle instance notes
that
a
> backup is being performed and internally compensates for it. As you know,
it
> is impossible to make an authentic copy of a database file that is being
> written to. Upon receipt of the command to begin the backup, however,
Oracle
> ceases to make direct changes to the database file. It uses a complex
> combination of rollback segments, buffers, redo logs, and archive logs to
> store the data until the end backup command is received and the database
> files are brought back to sync. .... What you should understand is that
the
> trade-off for taking a hot backup is increased use of rollback segments,
> redo logs, archive logs, and internal buffers within the SGA.
>
> You must be running the database in Archive mode to perform a hot backup.
> Archive logs assure data consistency when backing up only pieces of a
> database at a time.
>
> >>> "Eric Lansu" <eric.lansu_at_quicknet.nl> 06/20/00 09:11AM >>>
> Am I wrong, or am I wrong?
>
> But as far as I know you have to do a log-switch BEFORE starting the
> HOT-backup, and one AFTER the HOT-backup. The tape containing the
> database-files should also contain the archive-log-files created between
the
> log-switches. This way you can roll-forward (recover) the database to the
> point-in-time after completion of the backup, and thus bringing it all in
a
> consistent state. ( yes, yes, not from a book.... )
>
> Still the question remains; how can the OS make a copy of a datafile if
> Oracle is still writing in it? Better, how does Oracle know what to
update
> after recovery?
>
> Eric Lansu
>
> ----- Original Message -----
> To: "Multiple recipients of list ORACLE-L" <ORACLE-L_at_fatcity.com>
> Sent: Tuesday, 20 June 2000 11:03
>
>
> > Wow! your explanation is wonderful.
> >
> > Thanks Rachel.
> >
> >
> > Bhat
> >
> > -----Original Message-----
> > Sent: Tuesday, June 20, 2000 4:19 AM
> > To: Multiple recipients of list ORACLE-L
> >
> >
> > Lisa,
> >
> > I'm sorry but you are wrong. Writes to the datafiles continue during
hot
> > backup.....
> >
> > take a hypothetical situation:
> >
> > you have 3 redo logs
> > you have put every tablespace in your database into hot backup mode
> > you do a LARGE dataload (enough to cycle through all your redo logs
> several
> > times)
> >
> >
> > so... if Oracle does NOT write to the datafiles, then the changes you
> have
> > been making to the blocks get overwritten in the redo logs after the
logs
> > are archived. Once you take the tablespaces out of backup mode, given
> your
> > thinking, Oracle would have to then write all the blocks to the
database
> > files at once. But where would it get them from? The archived redo
logs
> are
> > NOT re-read, nor are the redo logs.
> >
> > So...... writing continues to the database files.
> >
> > Rachel
> >
> > >From: Lisa_Koivu_at_gelco.com
> > >Reply-To: ORACLE-L_at_fatcity.com
> > >To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com>
> > >Subject: Re: I/O activity during HOT backups
> > >Date: Mon, 19 Jun 2000 11:50:37 -0800
> > >
> > >No! The command below stops all writes to the datafiles in the
> tablespace
> > >for
> > >the duration of the backup, to ensure consistency.
> > >
> > >The i/o overload I see during backups is the data being copied out to
> our
> > >backup
> > >server. And it is usually very high: like 80% of all current
activity.
> > >
> > >Lisa
> > >
> > >
> > >
> > >
> > >
> > >Dan.Hubler_at_midata.com on 06/19/2000 01:18:14 PM
> > >
> > >Please respond to ORACLE-L_at_fatcity.com
> > >
> > >To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com>
> > >cc: (bcc: Lisa Koivu/GELCO)
> > >
> > >
> > >
> > >
> > >
> > >Please settle a discussion amongst our DBA team:
> > >
> > >Is there ANY I/O that takes place to the database files (*.DBF)
> > >during a HOT backup? (That is, ALTER TABLESPACE BEGIN BACKUP).
> > >
> > >If not, how does the process work?
> > >
> > >Thanks.
> > >
> > >
> > >
> > >
> > >???
> > >
> > >
> > >--
> > >Author:
> > > INET: Dan.Hubler_at_midata.com
> > >
> > >Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051
> > >San Diego, California -- Public Internet access / Mailing
Lists
> > >--------------------------------------------------------------------
> > >To REMOVE yourself from this mailing list, send an E-Mail message
> > >to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in
> > >the message BODY, include a line containing: UNSUB ORACLE-L
> > >(or the name of mailing list you want to be removed from). You may
> > >also send the HELP command for other information (like subscribing).
> > >
> > >
> > >
> > >
> > >
> > >
> > >--
> > >Author:
> > > INET: Lisa_Koivu_at_gelco.com
> > >
> > >Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051
> > >San Diego, California -- Public Internet access / Mailing
Lists
> > >--------------------------------------------------------------------
> > >To REMOVE yourself from this mailing list, send an E-Mail message
> > >to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in
> > >the message BODY, include a line containing: UNSUB ORACLE-L
> > >(or the name of mailing list you want to be removed from). You may
> > >also send the HELP command for other information (like subscribing).
> >
> >



> > Get Your Private, Free E-mail from MSN Hotmail at
http://www.hotmail.com
> >
> > --
> > Author: Rachel Carmichael
> > INET: carmichr_at_hotmail.com
> >
> > Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051
> > San Diego, California -- Public Internet access / Mailing Lists
> > --------------------------------------------------------------------
> > To REMOVE yourself from this mailing list, send an E-Mail message
> > to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in
> > the message BODY, include a line containing: UNSUB ORACLE-L
> > (or the name of mailing list you want to be removed from). You may
> > also send the HELP command for other information (like subscribing).
> > --
> > Author:
> > INET: LBhat_at_LEVI.com
> >
> > Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051
> > San Diego, California -- Public Internet access / Mailing Lists
> > --------------------------------------------------------------------
> > To REMOVE yourself from this mailing list, send an E-Mail message
> > to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in
> > the message BODY, include a line containing: UNSUB ORACLE-L
> > (or the name of mailing list you want to be removed from). You may
> > also send the HELP command for other information (like subscribing).
>
> --
> Author: Eric Lansu
> INET: eric.lansu_at_quicknet.nl
>
> Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051
> San Diego, California -- Public Internet access / Mailing Lists
> --------------------------------------------------------------------
> To REMOVE yourself from this mailing list, send an E-Mail message
> to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in
> the message BODY, include a line containing: UNSUB ORACLE-L
> (or the name of mailing list you want to be removed from). You may
> also send the HELP command for other information (like subscribing).
> --
> Author: William Beilstein
> INET: BeilstWH_at_obg.com
>
> Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051
> San Diego, California -- Public Internet access / Mailing Lists
> --------------------------------------------------------------------
> To REMOVE yourself from this mailing list, send an E-Mail message
> to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in
> the message BODY, include a line containing: UNSUB ORACLE-L
> (or the name of mailing list you want to be removed from). You may
> also send the HELP command for other information (like subscribing).
>
> ________________________________________________________________________
> Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com
>
> --
> Author: Vidya Kalyanaraman
> INET: kvidya13_at_hotmail.com
>
> Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051
> San Diego, California -- Public Internet access / Mailing Lists
> --------------------------------------------------------------------
> To REMOVE yourself from this mailing list, send an E-Mail message
> to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in
> the message BODY, include a line containing: UNSUB ORACLE-L
> (or the name of mailing list you want to be removed from). You may
> also send the HELP command for other information (like subscribing).
>
--
Author: Ruth Gramolini
   INET: rgramolini_at_tax.state.vt.us

Fat City Network Services    -- (858) 538-5051  FAX: (858) 538-5051
San Diego, California        -- Public Internet access / Mailing Lists
--------------------------------------------------------------------
To REMOVE yourself from this mailing list, send an E-Mail message
to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in
the message BODY, include a line containing: UNSUB ORACLE-L
Received on Wed Jun 21 2000 - 09:58:05 CDT

Original text of this message

HOME | ASK QUESTION | ADD INFO | SEARCH | E-MAIL US