TIP 71#: Number of concurrent users

One of my client got an renewal invoice from Oracle which tag price was based on 550 users.I got a call from the client which believed that having 550 concurrent users in beyond imagine.
Anyway to check number of concurrent users ?

There are 2 ways to check max number of concuurent user.

1. sessions_highwater in v$license shows the max number of concurrent user since last database startup.

2. If you are looking for details longer than last startup, Alert log shows the max number of concurrent users after each shutdown.
Here is a sample :

Shutting down instance (normal)
License high water mark = 3