Home » RDBMS Server » Backup & Recovery » How does RMAN recovery with its retention policy? (DB 10.2.0, RMAN catalog)
| How does RMAN recovery with its retention policy? [message #307438] |
Tue, 18 March 2008 21:37  |
trantuananh24hg
Messages: 744
Registered: January 2007
Location: Ha Noi, Viet Nam
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Senior Member |
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Good morning, every body!
Really, I am in a deviced mind as to what RMAN choose thing within the retention policy? With WINDOW RECOVERY OF 7 DAYS, which one backup will be marked obsolete when RMAN backup full?
Note that all of the backup full with all archivelog files.
Example
RMAN> list backup;
List of Backup Sets
===================
BS Key Type LV Size Device Type Elapsed Time Completion Time
------- ---- -- ---------- ----------- ------------ ---------------
4225 Full 17.17G DISK 00:28:51 08-MAR-08
BP Key: 4228 Status: AVAILABLE Compressed: NO Tag: TAG20080308T10124
8
Piece Name: /u03/backupVNP/BackupVNP_DB_17jao7p2_39_1
List of Datafiles in backup set 4225
File LV Type Ckp SCN Ckp Time Name
---- -- ---- ---------- --------- ----
1 Full 20045233644 08-MAR-08 /u03/oradata/VNP/system01.dbf
2 Full 20045233644 08-MAR-08 /u03/oradata/VNP/undotbs01.dbf
3 Full 20045233644 08-MAR-08 /u03/oradata/VNP/sysaux01.dbf
4 Full 20045233644 08-MAR-08 /u03/oradata/VNP/users01.dbf
5 Full 20045233644 08-MAR-08 /u03/oradata/VNP/users02.dbf
6 Full 20045233644 08-MAR-08 /u03/oradata/VNP/users03.dbf
7 Full 20045233644 08-MAR-08 /u03/oradata/VNP/rman.dbf
8 Full 20045233644 08-MAR-08 /u03/oradata/VNP/undotbs2.dbf
BS Key Size Device Type Elapsed Time Completion Time
------- ---------- ----------- ------------ ---------------
4312 459.10M DISK 00:00:25 08-MAR-08
BP Key: 4321 Status: AVAILABLE Compressed: NO Tag: TAG20080308T10422
9
Piece Name: /u03/backupVNP/BackupVNP_DB_18jao9gm_40_1
List of Archived Logs in backup set 4312
Thrd Seq Low SCN Low Time Next SCN Next Time
---- ------- ---------- --------- ---------- ---------
1 345 20044942149 08-MAR-08 20045348658 08-MAR-08
OKIE, those are the pieces of RMAN backup full, at 08/03/2008 - DD/MM/YY. They are not obsolete, but may be, at 20/03/2008 they will be obsolete. In the Oracle documents, the obsolete was identified by ....
| Quote: |
In other words, one backup of each datafile must satisfy the condition SYSDATE - CHECKPOINT_TIME >= RECOVERY WINDOW. All backups older than the most recent backup that satisfies this condition are obsolete.
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And I asked my self
What is the CHECKPOINT_TIME that RMAN identify?
Of course, if the RMAN identify CHECKPOINT_TIME, we must do it like, how do I?
And the second question:
If there are 2 backup full exist in the Destination_backup_folder, one was at 08/03, one was at 15/03. If I remove the 08/03_backup, may be the recovery processing will be failed. Why?
Please explain and make me more clarify.
Thank you very much!
[Updated on: Tue, 18 March 2008 21:44] Report message to a moderator |
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| Re: How does RMAN recovery with its retention policy? [message #307544 is a reply to message #307517] |
Wed, 19 March 2008 01:51  |
trantuananh24hg
Messages: 744
Registered: January 2007
Location: Ha Noi, Viet Nam
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Senior Member |
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Thank you, Michel, for your answer.
I know that, 2 backup 08 and 15 /03 will be not marked as obsolete piece in the RMAN's policy. But I wonder:
- One is 08/03, one is 15/03. Okie, assuming that DB will be recovered at 14/03, but, if DB crash at 14/03, there is no backup that I make, because the day is 14, not 15/03. I think that, RMAN find the neariest backup to restore and recover. With this situation, the backup is at 08/03.
- However, if I assume like that, there is no conception as hot backup. Now, the hot backup is understood easily like BACKUP DATABASE WHEN RUNNING, no more. Therefore, I think, Oracle server understands that, and how does it find the best way to do?
The way that RMAN does itself business is
+ Track the change of datafile, block by block
+ Keep the SCN that was updated into catalog/control_file
+ Modifies all of backup_datafiles before by new blocks.
....
According to the way, why does RMAN not choose the newest instead of the older backup?
Thank you!
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| Re: How does RMAN recovery with its retention policy? [message #307561 is a reply to message #307544] |
Wed, 19 March 2008 02:24 |
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Michel Cadot
Messages: 68718
Registered: March 2007
Location: Saint-Maur, France, https...
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Senior Member
Account Moderator |
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| Quote: | One is 08/03, one is 15/03. Okie, assuming that DB will be recovered at 14/03, but, if DB crash at 14/03, there is no backup that I make, because the day is 14, not 15/03. I think that, RMAN find the neariest backup to restore and recover. With this situation, the backup is at 08/03.
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But maybe it is 20/03 and you want to recover at 14/03 and not at 20/03, this is what means your retention policy: you want to be able to restore at any time in the past 7 days. If you just need to recover at the current time, you don't need such a policy.
Yes, RMAN takes the last avalaible backup to restore/recover a database unless you tell it to not doing so.
By the way, RMAN does not " Track the change of datafile, block by block"; it does not "Keep the SCN that was updated into catalog/control_file", this is done by the instance and is independent of RMAN...
Regards
Michel
[Updated on: Wed, 19 March 2008 02:26] Report message to a moderator |
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