1.at the time of creating connection string u could be enter username and password of ur db and click on test button,that helps whether u will able to connect ur db or not.
2.if u already created connection string,then try to pull some data,if u are able to see data on ur qv app..it's connecting else no.
If you want to check for connection errors at script execution time, you can set the ErrorMode variable to 0 and check for any ScriptError values different from 0. For example,
SET ErrorMode = 0;
OLEDB CONNECT YourConnectionParameters;
IF ScriptError <> 0 THEN
// Do something with this error condition
END IF
SET ErrorMode = 1;
See also the Error Variables chapter in QV Desktop Help.
