Applications Administration Guide > Activities >
About Configuring Owner and Employee Fields for Activities
Depending on your business process, you may want to configure the Siebel application so that the Employees and Owner fields for activities are always left blank when the activity is created. (The Owner field displays the primary from the Employee field.)
To achieve this, use Siebel Tools to set the predefault value of the Primary Owned By field (which maps to the Owner field that appears in the UI) in the Action business component to blank.