Hi Alex
How do you know the database/oracle8i isn't responding??? I'm not sure if you are running this on windows or Unix box (I only have experience with oracle on windows) If its windows you can go to services and see if you see an Oracle8i Services are running. The most important are The listener and the oracle8i instance name. I'm sure there is an equivalent in unix i just don't know it.
To shutdown the database and restart it you would have to log in to oracle as the administrator and issue a shutdown <immediate, normal> command normal is default.
To start it you would issue a startup there are other options but i don't think you would need them.
Again I only know oracle through windows I don’t expect it to be much different in Unix, just no GUI.