Finding Out Whodunnit Using The Transaction Log

David Fowler shows us how to figure out which user made a bad data change when you don’t have auditing mechanisms in place:

So it’s looking like things are in a bad way, obviously we could go to a backup and get the old values back but that’s never going to tell us who made the change.  So that transaction log again, how do we actually go about getting our hands dirty and having a look at it.

Well there’s a nice little undocumented function called fn_dblog.  Let try giving that a go and see what we get back. By the way, the two parameters are the first and last LSNs that you want to look between.  Leaving them as NULL with return the entire log.

This is great unless you have connection pooling and the problem happened through an application.  In that case, the returned username will be the application’s username.

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