Hi,
U can create profiles and assign to the users.In a profile u can limit how much CPU to be utilised by a call,a session,sessions per user etc.
U create a profile with the follwing command
sql> create profile developer
limit
sessions_per_user 3
cpu_per_call 6000/100 (hunderdts of a second)
cpu_per_Session 6000/100
idle_time 30
connect_time 60;

sql> alter user scott
profile developer;

Before assign the profile make a change to the init.ora file and bounce back the database.
RESOURCE_LIMIT=true

In case of any help please be free to ask me at [email protected]

Regards.
Rohit Nirkhe,Oracle DBA,OCP 8i
[email protected]