analyzing the tables corrects the problem.
I have seen a strange a thing happening with the application. The application is designed with certain database jobs that includes analyzing the tables and indexes on regular basis. I have observed that certain tables and indexes do not get analyzed daily.
When this happens, the application suffers hangs and some queries just do not work and end up with logging off the application user. When I manually analyze the tables and indexes using "alter table/ index ... compute statistics", then some queries start working fine and some others not.
The whole problem gets corrected when we restart both the database and application. Then the entire system works fine for few days before the problem starts recurring again.
Solaris 9 with Oracle 10g Release 1.