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Re: RMAN and NetBackup Performance

From: Mark Strickland <>
Date: Mon, 12 Mar 2007 10:03:45 -0700
Message-ID: <>

PARTIAL RESOLUTION After much drama with Symantec and much testing on my end, I figured out that you CAN use the "%t" format AND use an Oracle-managed Flash Recovery Area. The format has to be specific for the tape backups not for the backups to the FRA. I was trying to use it in my backups to the FRA. So, when you do RMAN backups to a Flash Recovery Area, don't specify a format for the RMAN backupset names. Just use the RMAN-supplied defaults. When you subsequently backup the FRA to tape, specify a format with "%t" at the end. Specifically, Symantec recommends this:


Whether you configure the tape channel(s) with this format permanently or specify it in the allocate command or in the backup command probably makes no difference. I'm doing it in the allocate command:

    allocate channel t1 type SBT format 'bk_%s_%p_%t';

My backups are now going as fast as they used to (or faster). With the "%" format, NetBackup is able to search the image catalog quickly. Without it, NetBackup starts at the most recent image file and works its way backwards in time all the way to the oldest image file. It does this because it has to verify uniqueness for the name of the backupset. In our case, for 90 days' worth of backups, we have 42,000 image files that have to be searched before and after the backup of the backupset. I did a simple test grep-ing through the image files for the name of one of my backupsets. It took 8 minutes. NetBackup can do it in about 6 minutes (without the benefit of the %t format). By that time, the tape has gotten ejected and has to be re-mounted. Another 1-2 minutes.

What I still don't understand (and maybe never will) is why my backups suddenly started taking a long time after 2/19. I'm still sending logs to Symantec. I can find nothing that changed on 2/19. The number of image files in the NetBackup catalog didn't suddenly grow exponentially. They were actually, day by day, dropping in number. At any rate, I do have a solution that works well. So, if you use RMAN and NetBackup, you might consider that same solution. Your tape backups may be taking much longer than they need to. I now know more about NetBackup logs than I ever cared to. If anyone would like a quick run-down of the logs, contact me offline. I'll be happy to share the misery.

BTW, compared to Symantec's support site, Metalink is a thing of beauty.

Mark Strickland
Seattle, WA

On 3/6/07, Mark Strickland <> wrote:
> Oracle RAC on Solaris9
> Symantec/Veritas NetBackup 5
> Anyone out there very experienced with managing RMAN with NetBackup?
> Starting the evening of February 19th, duration of the backups to tape of
> the Production Flash Recovery Area suddenly jumped from about 1/2 hour on
> average to 2-3 hours. These are level 1 incrementals. The actual backup
> time for each backupset is still 1-2 minutes as always, but there is a 5-7
> minute delay in between. Nothing has changed in terms of number/size of
> backupsets and total size of the backups. We opened a ticket with Symantec
> and we were instructed to turn on verbose logging for the various NetBackup
> processes on the RMAN client database server and NetBackup master server.
> I've become obscenely intimate with verbose NetBackup logs over the last two
> weeks. So far, not getting very far with Symantec. Their one contribution
> has been to suggest that we explicitly set the format for the RMAN backups
> with a %t at the end. This apparently is supposed to improve performance of
> NetBackup catalog lookups. In the RMAN docs, it says that if the format
> statement is used, Oracle will not manage the Flash Recovery Area
> automatically. So, that idea's out. I don't want to manage the FRA
> manually. After poring over NetBackup logs, we've determined that:
> The NetBackup image database for this particular RMAN client is quite
> large with about 42,000 image files totalling 47-GB. During each backup of
> an RMAN backupset, the image database is searched to see if a record for the
> RMAN backupset already exists. It starts with the most recent image file
> and works backward sequentially one-by-one through the 42,000 image files to
> the oldest image file (90 days ago, the retention period) even after it has
> already found the record for the backupset. That takes about 6 minutes,
> which is a long enough sleep for the NetBackup Scheduler to wake up and grab
> the opportunity to do a backup of the NetBackup catalog. Also, during this
> 6 minutes, the Media_Unmount_Delay has reached its default 180 second
> timeout, so NetBackup determines that the tape is no longer needed in the
> drive and ejects it. Finally, after the catalog search has come back and
> the same tape is re-mounted, 15 minutes have passed. Symantec had us
> disable automatic catalog backups and explicitly schedule them instead,
> which removed 6-8 minutes from the duration of the backup. What is left is
> the 6-7 minutes of searching the image database and remounting the tape.
> I can find nothing that changed on February 19th in our environment. The
> morning backups were of normal duration and the evening backups were not and
> the backups have been slow ever since. This is especially annoying because
> in early February, I increased MAXSETSIZE to get more data files into each
> backupset and reduce the number of backupsets from 100 to 15 which decreased
> the backups to tape from 3-1/2 hours to 30 minutes. We were quite enjoying
> that improvement.
> I've Googled and I've searched the Symantec site for clues. Nothing so
> far. Any ideas?
> Regards,
> Mark Strickland
> Seattle, WA

Received on Mon Mar 12 2007 - 12:03:45 CDT

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