Database Shutdown Modes

1-NORMAL
No new connections made on the database and oracle waits for all users to disconnect thier sessions, closes and dismounts database before instance shutdown, no instance recovery required upon next db startup.

2-IMMEDIATE
Rolls back all current uncommitted transactions and disconnects users sessions, closes and dismounts database before instance shutdown, no instance recovery required upon next db startup.

3-TRANSACTIONAL
No new connections, users disconnected when their current transactions are completed.

4-ABORT
All transactions are forcibly terminated, no transactions are rolled back, instance terminated without closing the data files, next startup will require instance recovery.