Hanging Sessions in Oracle 8.1.7

I have Oracle DB 8.1.7 with shared memory, no MTS, backward compatibility 8.0.5. We usually use import utility to create the schemas. The problem is that the database performance degrades after shutting it down and re-openning it dramatically with time. When a user's session is open he is frozzen untill another user connects to the database, only then that both sessions work and this phenomena repeates. Any suggestions?! Received on Sat Aug 03 2002 - 14:42:23 CDT