Database Performance Monitor - oratop

oratop is a database performance monitoring tool available for download from MOS. It has a interface similar to Unix/Linux top command. Oratop could also be used to monitor remote databases. It's RAC aware and gathers data from the internal views. Looking at the views that require select privilege this may also be used to monitor standard edition database as well as there are no views that require diagnostic or tuning license.
There are many options top tool by default list cumulative wait events

However this could be changed to list real time wait events as well.

There's nothing to install simply run the downloaded binary (after renaming it to oratop). Currently available for 11.2.0.3 - 11.2.0.4 and 12c.
Oratop is available for download from following MOS note
oratop - Utility for Near Real-time Monitoring of Databases, RAC and Single Instance [ID 1500864.1]