Comments on: Backing up to NUL vs Backup with Truncate only

By: Gail

Gail — Mon, 05 Mar 2012 21:04:13 +0000

Yes, absolutely. It’s like making normal log backups to disk then deliberately deleting one.

The only real use for a backup to NUL is when tweaking and tuning backups for best throughput.

By: suresh

suresh — Mon, 05 Mar 2012 15:35:42 +0000

Backup Log to Disk = ‘Nul’ is kind of dangerous then. You may keep doing log backups after it only to discover that they are of no use. So ideally its use should be avoided then? if we switch from “full” to “simple”, atleast while doing a log backup, we’ll come to know that it is not possible and log chain is broken.

By: Pradeep Singh

Pradeep Singh — Tue, 19 Oct 2010 11:57:01 +0000

Thanks for the Article Gail. I have used nul few times knowing that actual data wont be written to any file but you explain it better. Also, I didnt know the difference between backing log to nul and using truncate_only clause. Thanks again for excellent explanation.

By: Gail

Gail — Tue, 12 Oct 2010 20:05:29 +0000

I think you may want to read the post again, specifically the part that goes:

“Log backups will succeed after a backup to NUL. They’re useless for restoring the DB because there’s a log backup missing, but they’ll succeed.”

If you don’t want to retain log records for restore purposes, switch to simple recovery. You should only be in full if you’re retaining log backups for DR purposes and if that is the case, discarding a log backup (what this does) is WORSE than truncating the log because it’s only obvious what happened when you go to restore, which will likely be in a disaster situation

By: Vamshi

Vamshi — Tue, 12 Oct 2010 19:30:14 +0000

Thanks Gail, so nul can be used to truncate the log file, i,e empty in active transactions in the log and there is no need to take a full backup after this operation??

By: Weekly Link Post 110 « Rhonda Tipton’s WebLog

Weekly Link Post 110 « Rhonda Tipton’s WebLog — Sun, 13 Sep 2009 22:13:07 +0000

[...] Backing up to NUL vs Backup with Truncate only – A well written explanation. [...]

By: Gail

Gail — Tue, 08 Sep 2009 07:33:27 +0000

That’s null with 2 l’s. The NUL device has only 1.

Backup database master to disk = ‘null’ — creates a backup file named null

Backup database master to disk = ‘nul’ — backs up to the nul device, essentially deleting the backup

By: Simon

Simon — Tue, 08 Sep 2009 04:12:08 +0000

I did a backup xxx to disk = ‘null’ and then searched my disk and found a file name with null in the sql folder. It seem the null file specified is being treated as a filename??

By: Donovan

Donovan — Mon, 07 Sep 2009 13:54:11 +0000

Thanks again for very intuitive advice!

By: Dave Schutz

Dave Schutz — Sat, 05 Sep 2009 23:57:13 +0000

Gail,

Thanks for the excellent article. Sometimes it’s hard to keep up on the new features as well as features that are being deprecated.