Use of the Default User ID
If you do not supply the USER Authentication clause, the default user ID is used to attempt the connection.
The default user ID is the login name of the user running the application. In this case, you obtain network permissions with the standard authorization procedures. For example, on UNIX™, the default user ID must match a user ID in the trusted-host file (the /etc/hosts.equiv file or the file specified by the REMOTE_SERVER_CFG configuration parameter). On Windows™, you must be a member of the domain, or if the database server is installed locally, you must be a valid user on the computer where it is installed.