Asset Parent can be maintained from Asset Configuration History on the Maintenance Web Home (Self-Service) side of EAM.
To remove a parent relationtionship:
1. Go to the Assets tab of Maintenance Web Home page.
2. Navigate to the asset to be changed. S
3. Click the radio button for the asset in the search list, select "Configuration History" in the View drop-down then click Go.
4. Click the Show Parents radio button then click Go.
5. Find the active parent (null end-date) in the parent history list then click the update icon (pencil) on that row
6. Enter the end-date for the Parent relationship then click Apply.
Once removed, you can assign a new parent. I suppose Oracle may end-date the current parent for you if you associate a new parent to it but I haven't tested this theory.