>Hello Kamil:
>
> Thanks for you answer.But in my application each user have a application user name and password, they not use database user to login .

I use the same model as you. My users have a user name and a password to enter the application, and the application itself connects to a sql server. So the server's user name and a password are hidden from the user.
Both user names and passwords are stored in a scrambled form in a .dbf table, a record for each user. The record contains the application's user name/password and the sql server's user name/password.

Kamil