Differences Between the Startup and Shutdown Procedures

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PURPOSE ------- This article explains the differences in shutdown and startup procedures. SCOPE & APPLICATION ------------------- This is a tutorial for new Oracle DBAs. For the most complete information regarding database administration, please refer to the Oracle Server Administrator's Guide. STARTING AND STOPPING AN ORACLE DATABASE ---------------------------------------- The most common tool used to startup and shutdown the Oracle database from the command line is Server Manager. Beginning with Oracle8i, you can also use SQL*Plus. (If you want to use Oracle Enterprise Manager GUI tools, please refer to the Oracle Enterprise Manager Administrator's Guide for instructions.) You will have to login as a user with administrative privileges, specifically a user with SYSDBA privileges. Most DBAs are familiar with using the INTERNAL user (which is a synonym for the SYS user connected as SYSDBA) to startup and shutdown the database. In a future release of Oracle, however, the INTERNAL user will become obsolete. Therefore, you should setup your DBAs as SYSDBA users. Please refer to Note:50507.1 "TECH: SYSDBA and SYSOPER Privileges in Oracle8 and Oracle7" for more information about setting up privileged users. The Startup Procedure: ====================== There are three stages in starting an Oracle database: · Start the instance · Mount the database · Open the database You can control which stage by issuing different options on the STARTUP command. STARTUP NOMOUNT This will only start the Oracle instance. Oracle reads the initialization parameter file (init.ora) to determine where the control files are located, how large to create the System Global Area (SGA), and what background processes to create. When the instance is started, you will receive notification and a listing of SGA memory structures and sizes: ORACLE instance started. Total System Global Area 56011696 bytes Fixed Size 52144 bytes Variable Size 51785728 bytes Database Buffers 4096000 bytes Redo Buffers 77824 bytes STARTUP MOUNT This command starts the instance and mounts the database without opening it. Oracle reads control files for information about the data files and redo logs, but doesn't open the files. This is required when performing maintenance operations such as renaming datafiles, altering redo logs or enabling archiving. In addition to seeing the SGA listing, you will see "Database mounted." STARTUP This command starts the instance, then mounts and opens the database. The database opens online datafiles and online redo logs, and usually will acquire one or more rollback segments. You will see "Database Open" when the database is ready for normal database operations. If you use either STARTUP NOMOUNT or STARTUP MOUNT, you must use the ALTER DATABASE command to proceed opening the database. For example, from the NOMOUNT position (i.e., instance is started, but database is not mounted), you will need to issue two commands: ALTER DATABASE MOUNT; ALTER DATABASE OPEN; From the MOUNT state, you will only have to issue ALTER DATABASE OPEN. There are other options you can specify at startup: STARTUP RESTRICT The database will be opened, but only privileged users (users with the DBA role granted) can use the database. STARTUP FORCE This command does a combination of shutdown abort and startup. Use this only when experiencing problems in shutting down or starting the database. The Shutdown Procedure: ======================= There are four different shutdown options: SHUTDOWN NORMAL This is the default option for the SHUTDOWN command; therefore, you can issue SHUTDOWN, and your database will be shutdown NORMAL. No new connections are allowed after the statement is issued. Before the database is shutdown, Oracle waits for all currently connected users to disconnect from the database. The next startup of the database will not require any instance recovery. SHUTDOWN IMMEDIATE This option is used when you want to shutdown quickly, but still allow the database to shutdown cleanly. Current SQL statements being processed by Oracle are terminated immediately. Any uncommitted transactions are rolled back. (If long uncommitted transactions exist, the shutdown might not complete as quickly.) Oracle does not wait for users to disconnect; it implicitly rolls back active transactions and disconnects all connected users. SHUTDOWN TRANSACTIONAL This option is only available in version 8.1.X. Use this option when you want to perform a planned shutdown while allowing active transactions to complete. Any new connections or transactions will be denied. After all active transactions complete, the database will be shutdown as if an IMMEDIATE option was used. SHUTDOWN ABORT This option should only be used as a last resort. Use if: · The database is functioning irregularly and you cannot do a shutdown normal or shutdown immediate. · You need to shutdown the database instantaneously. · You experience problems starting the database instance. All current client SQL statements being processed will immediately terminate. Any uncommitted transactions will not be rolled back. Oracle does not wait for users currently connected to the database to disconnect, but will disconnect all connected users. The next STARTUP of the database will require instance recovery; therefore, the next startup may take longer than usual.