records not locking?

[Del]

After reading about this problem, I tried it here.
On a Windows 7, filePro 5.0.11 system, the system allowed me to get into
update mode on the same record at the same time from two different sessions.
I made a small change in the first session, saved it, verified the change, then
saved the same record from the second session with no changes, and this wiped
out the change from the first session.  There were no lookups involved, just
using dclerk update on the same record at the same time.
However, when I tried the same thing on my Unix system, an attempt to update
a record that was already being updated on another session gave me the message,
"Record Is Being Updated - Access Denied".
This difference between the Windows based system the the Unix based one is very
surprising (and disturbing!).
Am I doing something wrong, or is there an actual problem here?
Certainly don't want this happening at my client locations.

Del Neroni