Multiple EXEs using same datamodule

Hi,

        I'm trying to design a system and am new to Delphi. Since the system is
large, I wanted to break it down so that each module is an exe being called
by a controller that must remain open at all times (because it polls the
serial port for data being transmitted via barcode readers) and that must
update and read the databases at all times.

        All modules must access the datamodule as well, so is this system
structure possible? And if so, how is it done  so that the databases are
opened once and updatable by all modules even if 3, 4, etc... of them were
running at the same time? We're using Paradox databases.

Thank you,
Christine