You tried to execute a DBM server statement relating to a set user. However, this standard user has not been set in the DBM server.
First, set the required user using the DBM server statement dbm_userset. Alternatively, you can also specify a user/password combination explicitly when you re-execute the failed statement.
If the error occurs in the Database Manager GUI and there is no way in which you can correct it, contact your local support organization.