SHUTDOWN NORMAL
Normal database shutdown proceeds with the following conditions:
- No new connections are allowed after the statement is issued.
- Before the database is shut down, Oracle waits for all currently connected users to disconnect from the database.
- The next startup of the database will not require any instance recovery procedures.
SHUTDOWN IMMEDIATE
Use immediate database shutdown only in the following situations:
- A power shutdown is going to occur soon.
- The database or one of its applications is functioning irregularly.
- Immediate database shutdown proceeds with the following conditions:
- Any uncommitted transactions are rolled back. (If long uncommitted transactions exist, this method of shutdown might not complete quickly, despite its name.)
- Oracle does not wait for users currently connected to the database to disconnect; Oracle implicitly rolls back active transactions and disconnects all connected users.
The SHUTDOWN IMMEDIATE statement disconnects all existing idle connections and shuts down the database. If, however, you have submitted processes (for example, inserts, selects or updates) that are awaiting results, the SHUTDOWN TRANSACTIONAL statement allows the process to complete before disconnecting.
SHUTDOWN TRANSACTIONAL
When you wish to perform a planned shutdown of an instance while allowing active transactions to complete first, use the SHUTDOWN command with the TRANSACTIONAL option:
- After submitting this statement, no client can start a new transaction on this instance. If clients attempt to start a new transaction, they are disconnected. After all transactions have completed, any client still connected to the instance is disconnected. At this point, the instance shuts down just as it would when a SHUTDOWN IMMEDIATE statement is submitted.
- A transactional shutdown prevents clients from losing work, and at the same time, does not require all users to log off.
SHUTDOWN ABORT
You can shut down a database instantaneously by aborting the database's instance. If possible, perform this type of shutdown only in the following situations:
- The database or one of its applications is functioning irregularly and neither of the other types of shutdown work.
- You need to shut down the database instantaneously (for example, if you know a power shutdown is going to occur in one minute).
You experience problems when starting a database instance.
Aborting an instance shuts down a database and yields the following results:
- Current client SQL statements being processed by Oracle are immediately terminated.
- Uncommitted transactions are not rolled back.
- Oracle does not wait for users currently connected to the database to disconnect; Oracle implicitly disconnects all connected users.
