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RE: RMAN backup issue

From: Tom Tyson <tomtysonjr_at_yahoo.com>
Date: Thu, 2 Nov 2000 18:14:25 -0800 (PST)
Message-Id: <10668.121024@fatcity.com> 





Rao



To answer your question, first let me give Oracle's definitions of consistent
and incosistent:



Consistent:



A backup taken when the database is mounted (but not open)
and was not crashed or shut down with the ABORT option prior
to mounting. The checkpoint SCNs in the datafile headers
match the header information in the control file and none of the
datafiles has changes beyond its checkpoint. Consistent backups
can be restored without recovery.



Inconsistent:



A backup of any part of the target database when:

* It is open.
* It crashed prior to mounting.
* It was shut down with the ABORT option prior tomounting.


An inconsistent backup requires recovery to become consistent.



Going with those definition, a full backup must be taken in mount mode, and
therefore is not open for general use.  This allows a consistent image of all
used blocks to be backed up.  On the other hand, a incremental (ie. hotbackup)
only backups up the blocks that have changed since the last previous level. 
All incremental backups reguire at least one level 0 backup to base which
blocks have changed is all other subsequent backups.  And this of course is all
done while the database is up, and this is considered inconsistent.  The reason
it is inconsistent is because changes "can" happen when a database is open and
in order for that backup to be of use, you must apply archivelog files to make
it "consistent".



Hope that answers your questions, most of this stuff is in the Recovery
Manager's Guide on http://technet.oracle.com



Regards,


Tom Tyson


--- aaaa wwwwww <krisibm_at_lycos.com> wrote:


> Dear Tom

> 

> The only difference between a full backup and a incremental (differential /

> cummulative) backup is that one is consistent and the other is not

> 

> Can U please clrify this ?

> 

> Rao 

> 

> --

> 

> On Thu, 02 Nov 2000 15:35:24  

>  Rama Malladi wrote:

> >Tom,

> > Thanks for your mail. As I mentioned in my mail, After having a long

> >meeting, our team decided that to be on the safe side, it is good to have

> >both Full and Level0 on day1. We restored successfully several times after

> >that. But as you said it might have been redundant. Team decision at that

> >time was, it was okay to be on the safe side, even if it meant being

> >foolish!

> >

> > Coming to your questions...

> >

> >* Are you using a recovery catalog?

> >>> YES


> >

> >* Why are you placing your database in restricted mode for both scripts, the

> >"full" backup requires that your db in mount mode.. so no regular users can

> >log on, and the "level 0" to me, most likely should let your users work,

> >after all.. it is a hotbackup.. :)

> >>> We are doing the Hotbackups at 4am, when there are only batch jobs

> >running. No new sessions get started at that time. Infact, due to security

> >if anybody tries to login at that time, triggers will log them out

> >automatically. So we put it in Restricted mode.

> >

> >*  Why are you backing up the control file after the full backup?  Typically

> >this is only needed if you aren't using a recovery catalog, and need a

> >controlfile with the last backup info, is this the case?

> >>> Again to be on the safe side! If we lose all the 3 control files, we

> >thought we could get the old control file from the RCAT and mount the

> >database. Is there any otherway to mount the database, when all control

> >files are lost...?

> >

> >Thanks for your feedback

> >Rama

> >======================

> >

> >-----Original Message-----

> >Sent: Thursday, November 02, 2000 5:46 AM

> >To: Multiple recipients of list ORACLE-L

> >

> >

> >Just wanted to add my .02 cents...

> >

> >The only difference between a full backup and a incremental (differential /

> >cummulative) backup is that one is consistent and the other is not.  Another

> >difference is that the full backup causes every used block to get backed up,

> >but not unused blocks.  But you only need to apply archive log files to your

> >iconsistent database... Other than that, you can recover just as well.  I

> >have

> >had clients running for months with only Level 0's and 1's using a

> >incremental

> >cummultative backups with no problems.  I've had to perform db restores, and

> >had no problems recovering any part of the database.  A couple of questions

> >on

> >your scripts..

> >

> >* Are you using a recovery catalog?

> >

> >* Why are you placing your database in restricted mode for both scripts, the

> >"full" backup requires that your db in mount mode.. so no reqular users can

> >log

> >on, and the "level 0" to me, most likely should let your users work, after

> >all.. it is a hotbackup.. :)

> >

> >*  Why are you backing up the control file after the full backup?  Typically

> >this is only needed if you aren't using a recovery catalog, and need a

> >controlfile with the last backup info, is this the case?

> >

> >Anyway.. just thought I'd pipe in.. no offense meant..

> >

> >Tom Tyson

> >

> >

> >--- Rama Malladi <rmalladi_at_inteliant.com> wrote:

> >> Tom,

> >>  FYI.. I am posting both the Full as well as Level0 backup scripts that we

> >> have ... Still I am not sure if Level0 is same as Full or are they

> >> different.. After having a long meeting we all decided that to be on the

> >> safe side, it is good to have both on day1. Since then we do only Level1,2

> >> during the week and Level0 once a week.

> >>

> >> FULL


> >> ====

> >> {

> >> sql 'alter system enable restricted session';

> >> execute script alloc_disk;

> >> execute script defin_maxcorrupt_for_system;

> >> backup full

> >> skip offline

> >> skip readonly

> >> skip inaccessible

> >> tag Back_Fulldb_hsys

> >> filesperset 5

> >> format '/backup/oracle/arbor-106/Fulldb_arborora_%t_%s_%p.bs'

> >> (database);

> >> execute script rel_disk;

> >> sql 'alter system switch logfile';

> >> execute script arch_log_current;

> >> allocate channel c1 type disk;

> >> backup current controlfile format

> >> '/backup/oracle/arbor-106/Control_arborora_%t_%s_%p.bs';

> >> release channel c1;

> >> sql 'alter system disable restricted session';

> >> execute script back_all_alog;

> >> }

> >>

> >> Level0

> >> ======

> >> {

> >> sql 'alter system enable restricted session';

> >> execute script alloc_disk;

> >> execute script defin_maxcorrupt_for_system;

> >> backup

> >> incremental level 0

> >> skip offline

> >> skip readonly

> >> skip inaccessible

> >> tag Back_Hsys_Incremental_0

> >> filesperset 5

> >> format '/backup/oracle/arbor-106/Level0_arborora_%t_%s_%p.bs'

> >> (database);

> >> execute script rel_disk;

> >> sql 'alter system switch logfile';

> >> execute script arch_log_current;

> >> allocate channel c1 type disk;

> >> backup current controlfile format

> >> '/backup/oracle/arbor-106/Control_arborora_%t_%s_%p.bs';

> >> release channel c1;

> >> sql 'alter system disable restricted session';

> >> execute script back_all_alog;

> >> }

> >>

> >> *************************************************

> >> Rama Malladi, Sr. Oracle DBA

> >> Oracle Certified Professional (8 and 8i)

> >> Inteliant Corp., California

> >> RMALLADI_at_inteliant.com

> >> *************************************************

> >>

> >> -----Original Message-----

> >> blair_at_pjm.com

> >> Sent: Wednesday, November 01, 2000 8:11 AM

> >> To: Multiple recipients of list ORACLE-L

> >>

> >>

> >> RDBMS: 8.0.5


> >>

> >> We are using RMAN to backup a critical production 600G database.  We have

> >a

> >> successful level-0 backup and do level-1 backups 3 times a week.  To the

> >> best of

> >> my knowledge we have never done a "Full Backup".  Looking at the OEM Help

> >on

> >> topic "Backup" it looks like I don't need to do a full backup if I do

> >> level-0

> >> incrementals - but it is not clearly stated that way.  Am I correct?  Can

> >we

> >> forego Full Backups if we do Level-0 backups?

> >>

> >> ..tom

> >>

> >> --

> >> Please see the official ORACLE-L FAQ: http://www.orafaq.com

> >> --

> >> Author:

> >>   INET: blair_at_pjm.com

> >>

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> >> San Diego, California        -- Public Internet access / Mailing Lists

> >> --------------------------------------------------------------------

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> >> also send the HELP command for other information (like subscribing).

> >>

> >> --

> >> Please see the official ORACLE-L FAQ: http://www.orafaq.com

> >> --

> >> Author: Rama Malladi

> >>   INET: rmalladi_at_inteliant.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

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> >> (or the name of mailing list you want to be removed from).  You may

Received on Thu Nov 02 2000 - 20:14:25 CST












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