Some general portal caching questions

Hi experts,

I have some general questions regarding caching functions in portal.

1. In System administration->Navigation I can activate navigation cache. By default there are 3 connectors: Collaboration Connector, ROLES and gpn.

I guess Collaboration Connector caches Collaboration Content and Roles caches the content of the Role-based navigation? Is that correct? What is gpn-connector?

2. This cache does only cache the navigation structures? Not the iviews and the content?

3. For some iViews and pages I can activate caching in PCD with certain cache levels. That caching is not related to navigation caching?

4. I can't activate caching for web dynpro Java iviews and web dynpro java proxy pages. Is that corect? If not how can I achieve that. Those settings are deactivated for me, so I can't activate them.

5. In Visual Admin I can activate navigation cache under com.sap.portal.prt.sapj2ee. Is this option related to the setting I can set under system administration->navigation in portal? Because I avtivated the option in portal but in VA it still showed it as not activated.

I crawled some documentation but couldn't find exact information.

Thanks and regards

Manuel