How do I enable an existing WebLogic domain for OHS install in EM Managed Mode?

 Folks,

I have installed WebCenter Portal 11g.  The WebCenter installer creates its own WebLogic domain.  Now I want to install OHS in EM Managed Mode: the documentation only says that:

• Associating Oracle Instance with WLS domain

• Allows system components to be managed via EM (Enterprise Manager)

• A (JRF enabled) WLS domain needs to be pre-configured

     – Deploys system components’ MBeans in Admin Server

• Also loosely referred as “EM managed” mode

Do I need to extend the WebLogic domain with some particular features (such as Oracle JRF) before installing OHS?

This is a large scale deployment, and I would like to manage as much as possible through EM.