Hi Wayne,
Thanks for your reply!

>Sounds like an awful lot of trouble for nothing. If you use correct indexing, and parameterize your requests, I see no reason to keep them separate.
>
I will surely consider your oppinion. As I've mentioned in my original post, some of the lookup tables can be quite small (e.g. the currencies table which store the currencies known by my_apps and the current exchange rate; it won't exceed 10 rows but it will involve in most transaction).

>I would recommend not using MSDE in the scenario you describe anyway. From what you have mentioned, you might be pushing the limits of the MSDE database. I would suggest SQL Server - or going back to a VFP database.

I was worry about this too. But, the following is a post that made me think otherwise:
/start copy
As far as I know MSDE limit is not 5 users or connections but 5 concurrent
queries/batches. So it is not so important how many connections is used -
more important is how much the connections are busy.

From SQLServer2000 BOL -
"SQL Server 2000 Desktop Edition and SQL Server 2000 Personal Edition have a
concurrent workload governor that limits performance when more than 5
batches are executed concurrently. As the number of batches executing
concurrently increases, the governor lowers the performance of the system by
increasing amounts. Counts of the number of times more than 5 batches are
executed concurrently are maintained in internal counters. You can display
the contents of these counters using the DBCC CONCURRENCYVIOLATION statement
with either the DISPLAY parameter or no parameter. You should consider
upgrading to another edition of SQL Server 2000 if performance on a
well-tuned system is slow, and DBCC CONCURRENCYVIOLATIONS shows that the
database engine has often had significantly more than 5 batches executing
concurrently."
/end copy

I have SQL Server Developer Edition and I develop the apps using that. I will recommend the use of SQL Server with my product --- but in case my client won't invest in SQL Server (yet), then they can use MSDE as an alternatives.
I was thinking to go back to VFP DBC in the case I mentioned above. But, for me, to create an apps that can switch from VFP DBC to SQL Server in a snap (not to mention the data itself) is not an easy task. Yes, I know about CursorAdapter --- but still I have to create some code to 'upsize' the data. Moreover, if that's the case, I also have to create some code to maintain the database (all the PACK and PACK MEMO stuff). In a nutshell, *for me*, it's way too much to swallow.
Anyway, what do you think?

Looking forward to hearing more from you.
Thanks
Willianto