What does your data file look like?
All
of your Benchmark Libraries and Estimates are stored in a single
file. This file has a .df1 extension and looks like the
following:

As you
create more estimates your data file will expand in size and may
eventually split into segments; in this case you may end up with
multiple segments called .df1, .df2 etc. Whilst these are
separate files, Benchmark treats them as one continuous data
file.
What
is the T_Data File?
If
you use the Quantity Takeoff Sheet function, then Benchmark will
create a data file that is called T_xxx, where xxx is the name
of your data file. This data file stores all of your takeoff
sheet templates and completed takeoff sheets. You do not need to
open this file. If you do take a copy of your data file then you
should copy this file as well.
Creating a new data file without projects
Creating a new data file without any previous projects is
simple. To do this select the following option:

Backup your data file
Ensure that your data file(s) are stored on a server that is
backed up each night. If not you should manually take a backup
of your data regularly; you can do this by copying your data
file(s) or using Benchmark’s Backup feature (which can be seen
in the above screen shot).