At 10:01 30.10.2002 +0100, you wrote:

>A "Master" db containing the common tables, one or more "Service" db
>having the same "service" structure, contains 20 tables plus 10 tables
>that point to the Master db. The application builded from myself, at login
>time, asks for the name of the service, well, in the windows register,
>there is an association between the name of the service and the path of
>Service db. Every time my application has only two connection opened, one
>to the Master and another one to the Service db. Again, the customer can
>add as many service db as he want, without asking me for modify the code
>(or the db structure). He just create an empty Service db(copy, paste and
>rename and existing db) and the association in the register. Each service
>can modify any common table and the modification has to be visible to the
>other service.

What about having one generator GEN_SERVICE_DB and then add a field
ID_SERVICE_DB to all thirty tables to identify which of the services your
customer is currently working on? No more need for any copying of the
"Service" db, just a click to a button that grabs another ID_SERVICE_DB.
Then you would have in your database a table with the names of the
SERVICE_DB (and possibly the name of the user that created this SERVICE_DB,
in case other SERVICE_DBs should not be visible to other users) and its
ID_SERVICE_DB which the user can select from a LookupCombo or whatever.

HTH,
Set