An Approval Officer may delete sessions. An Editor may delete a session he currently owns. Your administrator will need to use the Clean Up Orphaned Versions tool in ArcCatalog to remove the associated ArcMap version data.
Delete in Session Manager:
    - Select the session to be deleted.
 
    - Click the Delete Session 
 button. 
    - A confirmation screen will verify that you want to delete the session.
        
            
        
     
    - Click Yes to delete or No to keep the session.
 
 
Delete in ArcFM or ArcFM Viewer for ArcGIS Engine:
    - Open the session to be deleted.
 
    - Click the Delete Session 
 button on the Session Manager toolbar in ArcFM or ArcFM Viewer for ArcGIS Engine. 
    - A confirmation screen will verify you want to delete the session.
 
    - Click Yes to delete or No to keep the session.
 
    - You may reopen Session Manager to see that the session has been removed. The corresponding version has been deleted as well.