Are you thinking of the Data Separation model? This is a method that puts all the interface elements in one file and the data in another. This is usually done to make updating your solution easier as you can replace older copies of the interface copy with new copies without having to import any data into the new file.
But to be especially safe when making design changes to your database, make the changes on a copy of your database kept off any servers and test any changes carefully and thoroughly. Then you can either deploy the updated copy to the server after importing any data that may or may not need to be imported or, for certain small changes--such as script and layout adjustments, you can open the hosted database and repeat the changes on the "live" database.
Making a copy of the database is exactly what I need to do, but will using 'Save copy as' under the file menu keep it off the server? Using Filemaker 10, btw.
Thanks a lot for your help.
By "server" do you mean that you are hosting the file with Filemaker Server?
If so, you cannot use Save a Copy as to make a copy of a file hosted over the network. You'll find that option is not enabled in that environment.
But you should be able to get a back up copy produced by a server scheduled back up and copy it over the network to your development machine. I use a shared directory on my development machine and remote desktop access to the server computer to copy back ups when I need to do so.
If you are not using FileMaker Server or hosting the file with FileMaker Pro, this would then seem to indicate that your file on the server is a file on a FILE server and this can imperil the safety of your database file as it can be easy to damage the file when used from a file server.