thanks
i.e user1 can connect to 8i and user2 can connect to 9i concurrently.
i.e. both homes can be active at the same time.

Also while installation do i need to create different user login (oracle) (linux) for 2 diffrent ORACLE HOME.
will i have to create 2 different listener.ora with diffrent port number for different ORACLE_HOME

if you know any documentation will you please give me a link
i am not able to see otn.