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MS Access backend backup

Posted on 2011-02-15
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An IT firm are currently setting up an automated backup system for one of my clients.
They are setting it up to do backups several times a day, including during working hours.

I pointed out to him that I'm unhappy about backups being done whilst the backend file is open.
This was his reply:

"The Symantec backup software use Microsoft Volume Shadow Copy Service backups - this is a point in time snapshot of the files - so it doesn't actually backup the file itself, it takes a copy of it.  This ensures the no lock-ups or database corruptions."

Is he right? Or is there still a risk of corrupting data?
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Question by:fionafenton
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Scott McDaniel (Microsoft Access MVP - EE MVE ) earned 1000 total points
ID: 34896510
Volume Shadow should be able to manage the backup with no interruption to your FE clients. As to whether that's a valid, reliable copy - that would depend on whether a user is writing to the database at the time of that copy or not. VSC can usually manage conflicts of this sort, but it's not infallible (but then no backup solution is infallible).

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by:peter57r
peter57r earned 1000 total points
ID: 34896848
I would say that this was a Q you need to direct to MS.

Historically Access has used 'deferred writes' - data isn''t written to disc immediately but stacks up changes and then writes them all.  This would seem fundamentally incompatible with VSS which as I understand it, sends a message to the application to 'flush all buffers' before taking its disk image copy.   This relies on the application (Access in this context, not YOUR application) being compatible with such requests.   SInce Volume Shadowing is a MS product it could be that all MS products are compatible with it, but I have no idea about that and I suspect there would be nothing publically documented anyway for Access.

The IT company may have more knowledge and so I think it would be wise to get a written assurance from them  that Access database applications can be recovered to points where all data would be consistent , without having to make any changes to the application, and not accept a general ' this is OK for everything' statement.  In this zone we frequently tell people not to take Access  backups while the file is open because of the risk of inconsistent data
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by:fionafenton
ID: 34897906
Thank you both. That gives me enough information to be going on with.
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Expert Comment

by:AccessYourBiz_Com
ID: 34898068
I have found that copying a file while it is open is generally ok. I have never had a problem doing that but I do not know if my environment is the same as yours. . To be sure you should do a test. Using a test database, create an update query (or something to write data) that will take at least 3 seconds, or long enough for you to initiate a copy of the file. Then run the query and initiate copying the file. Once the file is finished copying see if you can open the copy without any errors or corruption. Also close and re-open the source file to see if there is a problem.

Additional factors will be how many simultaneous users are accessing your BE data and also how large are the database files. Lastly, is this a 1000mbps network, 100Mbps and are there any wireless users? This can effect the success or failure. If you have small data files that are less then 10MB in size, they are much more forgiving. Especially if you have 10 or less simultaneous users. Furthermore, I've seen files 50MB in size with 10+ users work just fine on 1000mbps network if you are running nightly repair/compact routines on your data files.

Ultimately doing a test it the best way to determine if there is a concern.
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