What is the payroll EFT file UPDI{file creation number}.{bank number} used for

We recently had a change from our bank which required us to update the UPDIRECT.TXT payroll EFT file layout.  As a result of doing that, we discovered that our file server has another copy of the file in an area that is not locked down.  I was looking through the setup to see if the location for this file could be changed, but I have not found anything yet.  the file name is UPDI{the file creation number you enter when you create the EFT file}.{the bank number you assigned to the banking institution}.

I would like to know if it is used for anything and how long do we need to keep these files.

Thanks.

Jeff