Oracle hangs during importing

When an import session hangs, it is important that the underlying problem is
identified to be able to solve the problem.

First identify the session in the database serving the import :

select sid, user, program
from v$session
where upper(program) like '%IMP%';

Then verify the wait events for that session :

select sid, event, state, wait_time, seconds_in_wait
from v$session_wait
where sid = ;

This query will list the event that is being waited on, hence it will reveal
the underlying problem. Then act accordingly to solve the problem. Typically
this will be events like :