Oliver,
Are you putting this type in the comments at the top of an Entity bean class? What is the version attribute you are setting for Jonas? According to the documentation for XDoclet that tag is only available after version 2.4. Also make sure you have @jonas.bean ejb-name=”xxx” in your class comments. I tested this by just putting the following into the comments for a EJB CMP bean and also added the jonas subtask to the standard EJB configuration.
* @jonas.bean
* ejb-name="Person"
*
* @jonas.shared
* shared="true"
After I ran xdoclet, the jonas file contains the correct shared entry.