Hi,
System user type has two significant properties
- Dialog logon is not possible with this
-Security policy will not applicable for this user type( ex : password length, password expire time etc)
This id is most commonly used for RFC communications , BATCH Job configurations.
In security , Tcode will be assigned to users through roles and no risk involved in assigning access to system users.
Always options are there to track the actions of user if required.
Thanks,Krishna