You didn't say which job scheduler you are using, but generally speaking most scheduling software (OS/400, Robot, Maximise, etc) will allow you to specify a user ID that the job is to be submitted under. For example, the ADDJOBSCDE command for the OS/400 scheduler has a USER parameter that can contain *CURRENT (default), *JOBD or a user ID value.
The user ID specified will have to exist on the AS/400 otherwise the system won't have any idea of what authorities, etc are to be applied. The user ID will be put in the appropriate part of the SDS.
I'm not too sure on the value in the SDS for Web/ODBC connections. If I remember correctly, for ODBC connections you have to provide a user ID and password to make the connection, but the connection job runs under a QUSER or other system profile while the connection ID provided is used for authority checking, etc. I would hope that the connection ID would be placed in the SDS, but can't say for definite. Sorry.
All the best
Note that by specifying *JOBD for the scheduler job entry, you can change the user on the job description at any time in the future. When the scheduled job runs, it will run under the profile that is named on the job description at that time.
A user profile must exist in order to be named on a job description.
Also, CHGJOBSCDE USER( newname ) can simply change the scheduler entry at any time.