RE: BIG database backup methods
- From: "Mohan, Ross" <RMohan@xxxxxxxxxxx>
- To: <oracle-l@xxxxxxxxxxxxx>
- Date: Wed, 22 Sep 2004 15:19:47 -0400
RF -
We are considering using the "skip readonly" functionality in RMAN. ( Right
now, 8174. Soon, 9205. )
My **big** concern is the nightmare scenario where we set tspaces RO...get a
good backup...time
passes...system fails, requiring recovery...and <here a negative miracle
occurs> then we have
to not only lay down the RW and old RO files, but we have to replay all the
arc redo logs from
the oldest RO file on forward.
All of a sudden, we're in the position of having to apply thousands of arc
logs to recover a system.
The reason I bring this up is not abject ignorance (well, at least not
totally) but rather there's
a bug out there on precisely this issue (1530744 and 1373084 are relevant).
Have you seen this error?
Have you set up rolling tspaces to READ ONLY in VLDBs and backing them
up via "skip readonly" RMAN rcv files in your work? In your book? :-)
Thanks!
- Ross
-----Original Message-----
From: Freeman Robert - IL [mailto:FREEMANR@xxxxxxxx]
Sent: Tuesday, September 21, 2004 2:29 PM
To: 'Kline.Michael '; 'oracle-l@xxxxxxxxxxxxx '
Subject: RE: BIG database backup methods
There are a few options depending on your environemnt. Incremental backups
with RMAN can certainly reduce the size of your backup sets. Still, the
initial full backup is going to take some time to complete. How many tape
drives do you currently have access to? How long will it take to backup your
1-2 TB database to these drives? RMAN can parallelize the backup to many
drives, of course.
Also, compression can help as well. Early RMAN offers a quazi compression,
but 10g offers full blown compression (ala ZIP) which is most useful unless
the backup is getting compressed already (i.e. Your tape system does
compression).
I'm not sure about the data you have, but if you make your tablespaces read
only, then you only need to back them up once (and retain that backup of
couse).
Make sure management understands that recovery times will be impacted by
moving from disk to tape.
If you are new to RMAN check out my Oracle Press book, Oracle9i RMAN Backup
and Recovery.
Cheers!
RF
-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx
To: oracle-l@xxxxxxxxxxxxx
Sent: 9/21/2004 1:11 PM
Subject: BIG database backup methods
We have the "luxury?" of being able to do shadow copies for many of our data
warehouses. These are only in the 1-2 TB range, but with shadow copy, we
start at perhaps 2AM with the syncing, and then around 4PM we stop the
database, wait about 5 minutes, break the volumes and we're back up.
Management is getting very hungry looking at all these disks that are for
backup and thinking "If we used RMAN and went to tape it would be better...
I'm not so sure. 1-2 TB in 5 minutes is pretty good.
What are others doing?
Michael Kline
Database Administration
SunTrust Technology Center
1030 Wilmer Avenue
Richmond, Virginia 23227
Outside 804.261.9446
STNet 643.9446
Cell 804.744.1545
<mailto:michael.kline@xxxxxxxxxxxx> michael.kline@xxxxxxxxxxxx
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