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Query on RMAN backup retention policy [message #465689] Thu, 15 July 2010 04:37
Messages: 132
Registered: October 2009
Location: UK
Senior Member

I have a query regarding rman backup retention

I have tried to describe it and apologies for the terminologies/ conventions I have used, if it is not much clear.

I am taking backup of the database using the following script

configure controlfile autobackup on;
configure controlfile autobackup format for device type disk to '/u03/oradata/bkp/%F';
configure channel 1 device type disk format '/u03/oradata/bkp/%d_%T_%s_%p.bak';
configure retention policy to redundancy 2;
backup database plus archivelog;
crosscheck archivelog all;
crosscheck backup;
delete obsolete; # I have not written no prompt yet

There are 4 type of backups created with this

Step 1
Backup of archivelogs generated since previous backup till the archivelog generated due to log switch at the start of current backup

Step 2
backup of datafiles

Step 3
backup of archivelogs generated during backup

Step 4
Backup of controlfile

Now I am taking backup on say 1st, 2nd, 3rd and 4th day of a month (I will refer the backups as backup -1, backup -2, backup -3 and backup -4 respectively)

On 4th day while the backup - 4 starts following is backed up as Step 1
The archivelogs generated during backup - 2, till the one generated at the start of present backup (backup 4) are backed up

Subsequently step 2, step 3 and step 4 are followed

At the end of this backup (backup 4) following backups are deleted

(backup of datafiles in backup - 2)
(backup of archivelogs generated during backup - 2)
(backup of controlfile in backup - 2 )
(backup of archivelogs in step - 1 of backup -3, which contains archivelogs generated after backup 2 till start of backup -3)

Also at the end of this backup (backup 4) following archivelogs are deleted

(archivelogs generated during backup - 2)
(archivelogs generated after Backup -2 till the one generated at the start of backup - 3)

After this backup (backup 4) following backup were retained

Backup of datafiles in backup -3
Backup of archivelogs generated during backup - 3

Following are my questions on this

1) From above results, I got with retention policy as 2 (and the script above) can we say the earliest time I can recover is the time when backup - 3 finished? i.e. till previous backup

2) Since we are not retaining backup of datafiles in backup -2, why the archivelogs generated during backup -2, are backed up in backup - 4?

Thanks and Regards,

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