Objects That You Must Not Store in a Database
The following objects must remain in the types tag. You must not move them:
All built-in objects and their Siebel CRM Desktop equivalents, such as Contact, Email, To Do item, Calendar, and so on
All custom parent objects that Siebel CRM Desktop displays in the tree structure, such as Account or Opportunity
The Action object, which serves as a proxy for Calendar, To Do item, and Email items
The Attachment object, which requires special handling and cannot be moved