X Server access control problems
If you tried to run db2cc as a user diferent from the one who started the X server, you’ll probably get the error below:
Xlib: connection to ":0.0" refused by server
Xlib: No protocol specified
Assume x as the user that started the X server and y the other.
To avoid this you should run the folowing as x to give X server access to y:
xhost local:y