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RMAN : Slice Backup.
Category : ORACLE-SweetDreams - by webMaster_alaindereninfo
Oracle - "Sweet Dreams" - RMAN : Slice Backup.
Note: "Sweet Dreams are made of this..."
A "Sweet Dreams" article concerns an improvement, a new feature, that I would like to come alive in a next release of Oracle.
Abreviations:
IL0: Incremental Level 0. It's a Full backup of database, ready for performing Incremental backups later.
With RMAN, it's possible to perform Full or IL0 Backup of databases. IL0 permits to performs Incremental backup later.
The incremental mode is very powerful since the 10g, with the use of the Block Change Tracking.
I recommand the following steps:
a) One IL0 per week.
b) Incremental from 1 to 3 times a day, depending how sensitive the database is.
An example:
For a production database of 700Gb on idsk, the IL0 is around 80Gb in compressed mode and the duration of the backup is 1h10 to 1h25. And Incrementals twice a day, for a size of 1 to 4 Gb, for a duration of 1 to 3 mn.
This permits to have a very performing time for nightly batches during the week.
I imagine for RMAN, a new option, an incremental by slices.
To initialize the process, it just starts with an IL0 as usual for all incrementals.
Then, a number of Slice should be configured. For example, for 7 days, a slice a day, an IS (Incremantal Slice) should be launch by day. This a sort of incremental, where 1/7 of the database should be backuped entirely, and the rest in pure incremental. The day after, another 1/7 backup of the database should be done and so one.
In total, the 7 IS should be the equivalent of a full backup, and after rolling forward, no IL0 is necessary. Of course, between IS, it's still possible to perform simple incrementals.
Interests:
After an IL0 of 1h10 for example, it should have IS of 10mn, but each days. This allows to distribute the backup on time on each days of the week, and the volume of datas. It's no critical day of backup where the IL0 must be succesful.
Inconvenients:
To restore a database, all the "7" continuous slices must be available. If a slice is missing, the entire backup is not consistent.
But it's the same with the IL0 and Incrementals. If a incremental is missing, it's not possible to restore the database.
Creation date : 01/06/2011 : 11:37
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