Re: I/O activity during HOT backups

Lisa, I know those "low stress" days, I've had a few myself. You weren't the only one who didn't understand this... heck, there is a book out there that purports to be a wonderful reference on oracle that says the same thing

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 13:03:44 -0800
>
>Yup it's not unusual when I am wrong. I agree I am wrong. Stress level =
>130%
>today.
>
>
>
>
>
>"Rachel Carmichael" <carmichr_at_hotmail.com> on 06/19/2000 03:19:05 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)
>
>
>
>
>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
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> >--
> >Author:
> > INET: Lisa_Koivu_at_gelco.com
> >
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>--
>Author: Rachel Carmichael
> INET: carmichr_at_hotmail.com
>
>Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051
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>--
>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
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Received on Mon Jun 19 2000 - 19:45:06 CDT