How to update the database in rockbox after adding new songs ?
Go to Settings->General Settings->Database->Update Now
or set Auto update to yes (updates when you turn the player on)
or initialize the database
If you manually update while autoupdate is going on, you can mess things up a bit. Fix that by reinitializing.
I like how it updates the DB behind the scenes so I can continue listening to my music. No having to wait for it refresh for 5 minutes! Awesome!