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About Instance Shutdown

Instance shutdown is thc reverse of instance startup. When you shut down the Oracle instance. the default modę is a NORMAL shutdown. which means users are not allowcd

to crcatc new conncctions to thc databasc. but thc shutdown proccss waits for all currently connectcd users to cxit their sessions. After all the users havc disconncctcd. then thc committed transactions are written to disk. thc databasc files are elosed. and thc instance is stopped. Howevcr, therc are situations in which you may not want to wait for users to disconnect on their own (IMMEDIATE modę), or you want to let the currcnt transactions for each usercomplete before they are disconncctcd (TRANSACTIONAL modę). In emergency situations you can even shut down the databasc

without waiting for the committed transactions to be written to disk (ABORT modę). Shutting down an instance goes through thc following stages:

Sec Also:

■ "About Administrative Accounts and Privileges" on page 7-4 for morę information about the SYS and SYSTEM users, and the SYS DBA privilege

Shutting Down and Starting Up the Oracle Instance 5-8 Oracle Database 2 Day DBA

1.    After all the users have exited from their sessions, or been disconnected, Oracle Database writes data in the SGA to the data files and online redo log files. A chcckpoint is performed on the data files and their headers are marked currcnt as of the time of the instance shutdown. The data files and online redo log files are then elosed and the State of thc databasc is changed to CLOSED. The control file remains open to the instance.

2.    The Oracle instance dismounts the database and updates relevant entries in the control file to rccord a clean shutdown. The control file is elosed. The database is now elosed and dismounted. The instance is in the NOMOUNT State.

3.    The Oracle instance stops the background processes and deallocates the shared memory used by the SGA.

If a SHUTDOWN ABORT or abnormal termination occurs, then the instance of an open databasc closes and shuts down the databasc instantaneously. Oracle Database docs not writc data in the buffers of thc SGA to the data files and redo log files. The subsequentreopening of the databasc