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Understanding FRA Files [message #505770] Wed, 04 May 2011 16:23 Go to next message
eclipsis
Messages: 14
Registered: May 2011
Junior Member
Hello,

I have been experimenting with RMAN over the past few days and have a fairly strong grasp on it. I setup a test scenario using a three tier incremental approach as follows:


  • Every four weeks take level 0
  • Every 7 days take level 1
  • Every day take level 2


Obviously I'm only taking one per day, so on days I take a level 0, I'm not taking a level 1 or 2.

My scripts look similar to the following, with change to incremental level number.
rman target /  <<EOF
run {
configure device type disk parallelism 4 backup type to compressed backupset;
configure default device type to disk;
configure backup optimization off;
configure controlfile autobackup on;
configure retention policy to recovery window of 4 days;

backup incremental level 0 database plus archivelog delete input;

crosscheck backup;
crosscheck backup of archivelog all;
crosscheck backup of spfile;
crosscheck backup of controlfile;
delete noprompt obsolete;
}
exit;
EOF


What I'm trying to understand is what files Oracle is creating in the flash recovery area. I have several sets of files:

In the root level of the FRA, I see several files per incremental backup with names such as aambg4sa_1_1, aqmbg5mj_1_1, b6mbg614_1_1, etc. I was under the impression that these were the incremental backup pieces, multiple files because I'm using parallelism of 4.

Under a /FRA/<SID> I see 3 directories: archivelog, autobackup, and backupset. I assume arhivelog is where Oracle is archiving the redo logs, autobackup is storing the SPFILE and CONTROLFILE as I have enabled controlfile autobackup. However, what is being stored in backupset?

When I do a crosscheck, it lists the files within backupset, but does not list the several files under the root of FRA (b6mbg614_1_1 and so on).

What's the difference between /FRA/<SID>/backupset and the files under root FRA? Do I need both for recovery - and if not, why is Oracle keeping both?

I appreciate any help.
--Thanks!
Re: Understanding FRA Files [message #505776 is a reply to message #505770] Wed, 04 May 2011 16:58 Go to previous messageGo to next message
eclipsis
Messages: 14
Registered: May 2011
Junior Member
I think I may have figured out what is going on. Both sets of files are in fact backup sets. It seems the previous DBA had set the following:

CONFIGURE CHANNEL 1 DEVICE TYPE DISK FORMAT '/FRA/%U';
CONFIGURE CHANNEL 2 DEVICE TYPE DISK FORMAT '/FRA/%U';
CONFIGURE CHANNEL 3 DEVICE TYPE DISK FORMAT '/FRA/%U';

So my guess is that channel 4 was not defined and is going to the default /FRA/<SID>/backupsets directory. I'm going to clear out the config for channels 1 through 3 and try creating backups again. I would rather these all go into the default /FRA/<SID>/backupsets
Re: Understanding FRA Files [message #506072 is a reply to message #505770] Fri, 06 May 2011 07:13 Go to previous messageGo to next message
John Watson
Messages: 8922
Registered: January 2010
Location: Global Village
Senior Member
Quote:
Every four weeks take level 0
Every 7 days take level 1
Every day take level 2

Hi - one point you need to be aware of is that in 10g (according to the docs) there is no such thing as a level 2 incremental: you have only level 0, level 1, and level 1 cumulative. Specifying other levels does not throw an error, but I think this is for backward compatibility with 9i scripts. I could be wrong, but I believe you always get a level 1.
Re: Understanding FRA Files [message #506109 is a reply to message #506072] Fri, 06 May 2011 09:34 Go to previous messageGo to next message
eclipsis
Messages: 14
Registered: May 2011
Junior Member
Hmm, so if that's the case, I'd really be taking level 1 every day. It seems the alternative is to change to the following strategy:



  • Every four weeks take level 0
  • Every week take level 1 cumulative
  • Every day take level 1 differential


However, according to the docs for 10gR2 (download.oracle.com/docs/cd/B19306_01/backup.102/b14192/bkup004.htm):

Quote:
A level 1 incremental backup can be either of the following types:

* A differential backup, which backs up all blocks changed after the most recent incremental backup at level 1 or 0
* A cumulative backup, which backs up all blocks changed after the most recent incremental backup at level 0


So this means during week 3, my second level 1 cumulative backup, it would be capturing all changes from the original level 0, not the first level 1 cumulative? This would benefit restore by not requiring two level 1 cumulative but would slow down backup.
Re: Understanding FRA Files [message #506116 is a reply to message #506072] Fri, 06 May 2011 09:53 Go to previous messageGo to next message
NehaMemory
Messages: 5
Registered: May 2011
Location: Bangalore
Junior Member
We may have backups upto level n-as far as I have seen.
Re: Understanding FRA Files [message #506119 is a reply to message #506116] Fri, 06 May 2011 09:56 Go to previous messageGo to next message
BlackSwan
Messages: 26766
Registered: January 2009
Location: SoCal
Senior Member
>We may have backups upto level n-as far as I have seen.
perhaps true, but can you successfully restore Oracle RDBMS from them?
Re: Understanding FRA Files [message #506120 is a reply to message #506119] Fri, 06 May 2011 10:00 Go to previous messageGo to next message
eclipsis
Messages: 14
Registered: May 2011
Junior Member
According to the 10gR2 docs, only options are incremental level 0, incremental level 1 (differential), and incremental level 1 (cumulative). It seems higher incremental levels will run without error, but will simply be treated as a level 1. So to be on the safe side, I think I'll move to level 0 monthly, cumulative level 1 weekly and differential level 1 daily.

I'm assuming the block change tracking will apply for each of the cumulative level 1 so a full file scan is not necessary. This block change tracking is reset with each level 0?
Re: Understanding FRA Files [message #506121 is a reply to message #506120] Fri, 06 May 2011 10:06 Go to previous messageGo to next message
BlackSwan
Messages: 26766
Registered: January 2009
Location: SoCal
Senior Member
>I'm assuming the block change tracking will apply for each of the cumulative level 1 so a full file scan is not necessary.
You are free to assume anything your desire.

Do you have a tested & documented Restoration Procedure that guarantees a successful restoration?
Re: Understanding FRA Files [message #506122 is a reply to message #506121] Fri, 06 May 2011 10:09 Go to previous message
eclipsis
Messages: 14
Registered: May 2011
Junior Member
This was meant as more of a question. Will the block change tracking file be used for each level 1 cumulative backup - eliminating the need for a full scan of all blocks? Is it reset at each level 0?

Either way this won't impact restore/recovery? It will only speed up the level 1 backup process by reducing read/scan time.
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