RE: RMAN backups

When I first installed 9.2.0.4 from 8.0.6.3 my backups (of the migrated databases) went up from 1 to 6 hours (roughly). Oracle could not tell me why. However, when I did a complete restore/recovery of the databasess in question the backup time went back to about 1 hour. I have my own ideas as to why but no definitive answer from Oracle. You could try to do a complete restore or duplicate the databases and see if that helps. YMMV!

Regards,
Ruth

-----Original Message-----

From: Allen, Brandon [mailto:Brandon.Allen_at_OneNeck.com] Sent: Tuesday, June 21, 2005 1:44 PM
To: rgramolini_at_tax.state.vt.us; jrsmiley_at_gmail.com; richard.ignizio_at_paetec.com
Cc: oracle-l_at_freelists.org
Subject: RE: RMAN backups

I think the results I have shown below, although accurate, may be misleading. After further analysis I noticed that when we first implemented incrementals, the backup time was not much shorter than for the full backups, however something changed in January that made the backup time for the Full backups rise sharply, while incrementals remained consistent. I'm working with my tape library admins to see what may be the cause and will reply later with my findings. In the mean time, please do not expect your backup time to be dramatically reduced by implementing incrementals like I have shown below - I believe there is some other force at work here besides just the incremental vs. full difference. It may be something simple like the tape library is busy with replication on Thursdays when we run our Full backups or something like that.

Regards,
Brandon

-----Original Message-----

From: Allen, Brandon
Sent: Tuesday, June 21, 2005 10:17 AM
To: 'rgramolini_at_tax.state.vt.us'; jrsmiley_at_gmail.com; richard.ignizio_at_paetec.com
Cc: oracle-l_at_freelists.org
Subject: RE: RMAN backups

We do save a significant amount of time and space by using incremental backups:

SQL>select avg(elapsed_seconds)/60/60 from rc_backup_set where db_key=2300 and backup_type='D' and completion_time >= sysdate -45;

AVG(ELAPSED_SECONDS)/60/60

                 3.8742284

SQL>select avg(elapsed_seconds)/60/60 from rc_backup_set where db_key=2300 and backup_type='I' and completion_time >= sysdate -45;

AVG(ELAPSED_SECONDS)/60/60

                1.13801519

Regards,
Brandon

-----Original Message-----

From: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org]On Behalf Of Ruth Gramolini
Sent: Tuesday, June 21, 2005 10:05 AM
To: jrsmiley_at_gmail.com; richard.ignizio_at_paetec.com Cc: oracle-l_at_freelists.org
Subject: RE: RMAN backups

John,

Unless something has changed with 10g, and incremental backup doesn't actually save much time. Rman still has to read the block headers to see if the block needs to be backed up. It mostly saves space on disc if backing up to disk.

Correct me if I am wrong!
Ruth
-----Original Message-----

From: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org]On Behalf Of John Smiley
Sent: Saturday, June 18, 2005 11:19 AM
To: richard.ignizio_at_paetec.com
Cc: oracle-l_at_freelists.org
Subject: Re: RMAN backups

Backup times with RMAN are going to vary greatly depending upon the hardware and how many blocks need to be backed up. Even a very large database can be backed up incrementally if very few blocks have changed since the last backup with RMAN.

What might be a better yardstick is backup rate. The fastest RMAN backup rate I've seen was published by Amazon a few years back. They attained 2TB / hour.

John Smiley
Technical Management Consultant
TUSC, Inc.

Privileged/Confidential Information may be contained in this message or attachments hereto. Please advise immediately if you or your employer do not consent to Internet email for messages of this kind. Opinions, conclusions and other information in this message that do not relate to the official business of this company shall be understood as neither given nor endorsed by it.

--
http://www.freelists.org/webpage/oracle-l