Discussion yesterday: "OEM Grid Control / Cloud Control is expensive! You have to pay for the Packs to make it useful. You don't need to pay for the Diagnostics Pack in Database Control."
Sorry folks - that is totally incorrect.
The DB Diagnostics Pack and the SQL Tuning Pack (as well as other packs) are options added to the database. To use them, you need to pay for them.
These packs happen to collect information. Accessing that information (using the views) requires a license, and [in production] you (usually) need to pay for that license.
It does not matter whether you use Database Control or Grid/Cloud Control to display the contents of those views as rows/columns, or as alert messages, or as charts or graphs. You still need to license it.
From the Database side, see the Licensing document at the doc home page (for 11gR2 see http://www.oracle.com/pls/db112/homepage).
From the OEM side, see the Licensing document found through ttp://docs.oracle.com (for 12c, see http://docs.oracle.com/cd/E24628_01/index.htm)