Re: Oracle: how to demonstrate successful restore?

From: Mladen Gogala <gogala_at_sbcglobal.net>
Date: Sat, 28 Jan 2006 05:05:37 GMT
Message-Id: <pan.2006.01.28.05.05.34.928042@sbcglobal.net>

On Fri, 27 Jan 2006 21:46:23 +0100, Frank van Bortel wrote:

> But you will be surprised how few companies actually
> test their DR plan...

It's a business decision. What surprises me is how few people actually verify their backups. Here is it all it takes: RMAN> restore database validate;

Starting restore at 27-JAN-06
allocated channel: ORA_DISK_1
channel ORA_DISK_1: sid=64 devtype=DISK

channel ORA_DISK_1: starting validation of datafile backupset
channel ORA_DISK_1: reading from backup piece /oradata/back/back_01h9uj59_1_1.bkp
channel ORA_DISK_1: restored backup piece 1

piece handle=/oradata/back/back_01h9uj59_1_1.bkp tag=TAG20060127T232632 channel ORA_DISK_1: validation complete, elapsed time: 00:01:06 Finished restore at 27-JAN-06

My database wasn't actually restored, only the backup was validated. Here is the problem, visible in sar output while the validation is running: $ sar -u 5 10
Linux 2.6.12-1.1381_FC3 (medo.noip.com) 01/27/2006

11:51:53 PM       CPU     %user     %nice   %system   %iowait     %idle
11:51:58 PM       all     99.00      0.00      1.00      0.00      0.00
11:52:03 PM       all     99.00      0.00      1.00      0.00      0.00
11:52:08 PM       all     99.00      0.00      1.00      0.00      0.00
11:52:13 PM       all     99.00      0.00      1.00      0.00      0.00
11:52:18 PM       all     16.03      0.00      1.40     82.57      0.00
11:52:23 PM       all      2.59      0.00      1.60     95.81      0.00
11:52:28 PM       all      1.61      0.00      0.60     97.79      0.00
11:52:33 PM       all      0.40      0.00      0.80     98.80      0.00
11:52:38 PM       all      0.40      0.00      0.20     99.40      0.00
11:52:43 PM       all      2.20      0.00      1.40     96.40      0.00
Average:          all     41.94      0.00      1.00     57.06      0.00

Validation was active during the first few snapshots. It's extremely expensive operation, especially if the backupset is compressed. Without the compression, it takes approximately 40% of the CPU, but it is an expensive operation, even on the much bigger machines then my measly PC. Probably people think that not having a backup or having a bad backup is cheaper then verifying it? You are a DBA in the Big Easy, no snow, no ice storms, what could ever happen to your database? It's unlikely that it will ever be sleeping with the fishes, to use the term from "Godfather"? Why verify?

-- 
http://www.mgogala.com

Received on Fri Jan 27 2006 - 23:05:37 CST