Concurrent Operations

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Concurrent Operations

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OzYbOi d(-_-)b SSCarpal Tunnel Points: 4054 More actions · Answer 1

OzYbOi d(-_-)b

SSCarpal Tunnel

Points: 4054

December 15, 2011 at 8:49 am

#1422007

Thanks Steve

David Burrows SSC Guru Points: 65111 More actions · Answer 2

Hugo Kornelis (12/15/2011)

If you really want to test the statement made in today's question, you have to run the two backup commands from two seperate tabs in SSMS

Out of curiosity (I guessed wrong :crying:) I did a test using WAITFOR,SELECT GETDATE();BACKUP;SELECT GETDATE() in two separate SSMS query windows

both started at the same time, completing without error and taking 0.58 secs, one finished after 0.58 secs from start the other after 1.2 secs

Far away is close at hand in the images of elsewhere.
Anon.

Hugo Kornelis SSC Guru Points: 64748 More actions · Answer 3

David Burrows (12/15/2011)

Hugo Kornelis (12/15/2011)

If you really want to test the statement made in today's question, you have to run the two backup commands from two seperate tabs in SSMS

Out of curiosity (I guessed wrong :crying:) I did a test using WAITFOR,SELECT GETDATE();BACKUP;SELECT GETDATE() in two separate SSMS query windows

both started at the same time, completing without error and taking 0.58 secs, one finished after 0.58 secs from start the other after 1.2 secs

I did a similar test. In my case, both backup statements claimed an execution time of approximately 3 seconds, but SSMS told me that one of the two windows had an actual execution time of 6 seconds. And because I had sp_who2 ready to submit in a third tab, I was also able to see the second process waiting for the first. (I did not run sp_lock, so I don't know what kinds of locks are involved in this case).

Hugo Kornelis, SQL Server/Data Platform MVP (2006-2016)
Visit my SQL Server blog: https://sqlserverfast.com/blog/
SQL Server Execution Plan Reference: https://sqlserverfast.com/epr/

TomThomson SSC Guru Points: 104773 More actions · Answer 4

I sometimes like questions where I have to guess what they mean, but sometimes I don't. Here I didn't, even though I eventualy got it right.

These were the questions that had to be answered: did whoever wrote the question mean both backups to be of the same database? If so he was maybe sloppy because he didn't say so, so was he misusing "concurrent" to include one working while the other was queued waiting for it to finish?

But not a bad question, I guess. People who read the explanation can learn from it. I for one have learnt from it. I was unaware of the BoL page referenced and I only got this question right because I had misunderstood the concurrency section of the backup page as saying that neither backup database nor backup log could be concurrent with backup filegroup - but this reference shows that backup log can be concurrent with backup file group, so this question has disabused me of a belief I've held for years (since I first started evaluating SQL 2008).

Tom