The Is data file locked command returns True if the data file of the open database or at least one of its segments is locked — i.e. write protected.
Placed, for instance, in the On Startup database method, this command enables the prevention of any risk of accidental opening of a locked data file.
This method will prevent the opening of the database if the data file is locked:
If(Is data file locked)
ALERT("The data file is locked. Impossible to open database.")
QUIT 4D
End if