The SYSMAN schema in your OEM repository contains near-real time data from all of your EM targets. These two queries have been very useful in my enterprise whenever someone asks the inevitable “Which physical host is XYZ database running on?” or “Can I get a list of all the production databases?”
When you extend these queries to include external tables for specific target properties (SOX databases, f.e.) you can provide a link to your customers or team and save your cycles for something more challenging.
The database inventory includes a call to my local SCOOP schema view using the second query.