Every now and then I get an email asking me if I can remove some of the databases on server ‘X’ that have not been used in quite some time. I am always curious as to how someone has already ascertained that the database has not been used so I ask them the question and I have lost count of the number of times I have been greeted with this response:
“Oh, that’s simple, I just look at the modified date for the data files in Windows.”
Um…what? Look, let’s leave the database administration to the professionals and you can just go back to whatever it was you were doing before. I beg of you, do not delete or drop a database based upon the modified date on the data files in Windows. Then again, go ahead, and drop me an email when you need me to help you clean things up, my rates are quite reasonable.
Just to be clear on this: that date only changes on specific actions. If the file was recently expanded (or auto-grow), or shrunk (shudder), or perhaps the database was restored (or reattached like a finger). All of those actions would change the modified date in Windows.
SELECT statements would not alter the modified date. Nor would a DELETE, or an UPDATE, but an INSERT might if it caused the file to expand. I wish I had a comprehensive list of actions that would cause the modified date to be changed but it is easier to remember the things that do not change that date and go from there.
So, bottom line is that the modified date has nothing to do with actual database usage. If you are thinking of removing databases based upon the modified date…well…please don’t.