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@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx]On 
Behalf Of Ruth Gramolini
Sent: Tuesday, June 21, 2005 10:05 AM
To: jrsmiley@xxxxxxxxx; richard.ignizio@xxxxxxxxxx
Cc: oracle-l@xxxxxxxxxxxxx
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@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx]On 
Behalf Of John Smiley
Sent: Saturday, June 18, 2005 11:19 AM
To: richard.ignizio@xxxxxxxxxx
Cc: oracle-l@xxxxxxxxxxxxx
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.

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