1. Closing the database requires permissions: SYSDBA or SYSOPER.
2. Tools for closing the database: SQL* PLUS or SRVCTL.
3. Four modes of closing the database: normal (sql * plus tool default), immediate (srvctl tool default), transactional And abort.
Normal mode:
New connection is not allowed, waiting for the end of the original connection. If the system currently has long transactions or long connections, it will take too long to close the database. Generally not used.
Immediate mode:
New connections are not allowed, and user connections are actively disconnected. If there are transactions on the current connection, rollback the uncommitted transactions.
Transactional mode:
New connections are not allowed, waiting for the end of the current transaction, and after all transactions are over, the connection is disconnected.
Abort mode:
New connections are not allowed and user connections are actively disconnected, the transaction is ended immediately (not rolled back), and the client SQL statement processing is ended immediately.
Note: The about mode is likely to cause data inconsistencies. The next time you start the instance, you need to restore the instance!