I'm not sure of what the implications are of doing shutdown immediate vs. the normal procedure.
There's a couple of kinds of shutdown:
- Normal : wait for clients to disconnect before completing a shutdown. This is a clean shutdown
- Transactional : wait for clients to complete any pending transactions before completing a shutdown. This is also clean
- Immediate : terminate and rollback and pending transactions. This is also clean
- Abort : shutdown now. This is an unclean shutdown, and will require "instance recovery" (cleanup of the mess any previous transactions have made) next time Oracle is started.
Andy is right that life is happier if you shutdown the db clients before you shutdown the database. If you have just a few clients, that's usually not too big of an issue.