1) to check if the db user already functioning , please login on the db using it on the sql server first .
2) Rerun the commands mqsisetdbparams and after successfull command initiation use mqsicvp to check if the connection to the DSN is successfully intaited or not as the mqsisetdbparams if written correctly with correct flags will return success but don't checks for the validation of these credentials .
3) mqsistop and mqsistart for the integration node .