The convenient database engine for a "Distributed" System

[dcrespo]

Hi all...
Here is my infrastructure design of a "distributed" system:
- Many (30-50) hosts connected via VPN to a server.
- Each host manages a system that receives local data (stored in a
local database), and has to be sent to the server, so the rest of the
hosts can "see" this data.

What I want? I want to have a
portable/changeable/easy-installation/cross-platform local database.

The problem is that the database structure may change, so I have to
change the database structure of each host. As you can see, it requires
the database structure to be very portable and changeable.

I think there is 2 database paradigms to consider: The Access-like one,
and the MySQL-like one. With the Access-like paradigm, it only needs
the file .mdb on the local host, and its respectively set of dlls to
manipulate it. But, I remember that I need a cross platform database...
On the other hand, the MySQL-like paradigm, needs the database engine
to be installed for running. The cons of it, is that is more difficult
(I don't know yet if a can do it) to install it silently, I mean
without user intervention, whereas  a .mdb file being a member of the
system installation files is totally viable.

I heard about sqlite... Any comments?