DESCRIPTION
You can find all users currently logged into Oracle by running a query from a command prompt. In Oracle/PLSQL, there is a system view called V$SESSION which shows the session information for each current session in the database. You can run a query against this system view to return all users that currently have a connection running in the Oracle/PLSQL database.
SYNTAX
The syntax to retrieve the users logged into Oracle is:
SELECT USERNAME FROM V$SESSION;
This SELECT statement will return each username that is logged in.