SHUTDOWN NORMAL
1)No new connections are allowed after the statement is issued
2)Before the database is shut down, Oracle waits for all currently connected users to disconnect from the database.
3)The next startup of the database will not require any instance recovery procedures.

SHUTDOWN IMMEDIATE
1)Current client SQL statements being processed by Oracle are terminated immediately.
2) Any uncommitted transactions are rolled back.
(IF LONG UNCOMMITTED TRANSACTIONS EXIST, THIS METHOD OF SHUTDOWN MIGHT NOT COMPLETE QUICKLY , DESPITE ITS NAME.)
3)Oracle does not wait for users currently connected to the database to disconnect;
4)Oracle implicitly rolls back active transactions and disconnects all connected users.
5)The next startup of the database will not require any instance recovery procedures.

SHUTDOWN ABORT
1)Current client SQL statements being processed by Oracle are immediately terminated.
2) Uncommitted transactions are not rolled back.
3) Oracle does not wait for users currently connected to the database to disconnect.
4)Oracle implicitly disconnects all connected users.
5)The next STARTUP of the database will require instance recovery procedures; however, instance recovery will be automatically performed during database startup.

Ramesh...