When you start up a database, you create an instance of that database and you determine the state of the database. Normally, you start up an instance by mounting and opening the database. Doing so makes the database available for any valid user to connect to and perform typical data access operations. Other options exist, and these are also discussed in this section.
This section contains the following topics relating to starting up an instance of a database:
Options for Starting Up a Database
You can start up and administer an instance of your database if several says, as described in the sections that follow.
Starting Up a Database Using SQL*Plus
You can start a SQL*Plus session, connect to Oracle Database with administrator privileges, and then issue the STARTUP command. Using SQL*Plus in this way is the only method described in detail in this book.
Starting Up a Database Using Recovery Manager
You can also use Recovery Manager (RMAN) to execute STARTUP and SHUTDOWN commands. You may prefer to do this if your are within the RMAN environment and do not want to invoke SQL*Plus.
Starting Up a Database Using Oracle Enterprise Manager
You can use Oracle Enterprise Manager (EM) to administer your database, including starting it up and shutting it down. Enterprise Manager is a separate Oracle product that combines a GUI console, agents, common services, and tools to provide an integrated and comprehensive systems management platform for managing Oracle products. EM enables you to perform the functions using a GUI interface, rather than command line operations.
The remainder of this section describes using SQL*Plus to start up a database instance.
Preparing to Start an Instance
You must perform some preliminary steps before attempting to start an instance of your database using SQL*Plus.
Now you are connected to the database and ready to start up an instance of your database.
Using SQL*Plus to Start Up a Database
You use the SQL*Plus STARTUP command to start up an Oracle Database instance. To start an instance, the database must read instance configuration parameters (the initialization parameters) from either a server parameter file or a traditional text initialization parameter file. When you issue the STARTUP command, by default, the database reads the initialization parameters from a server parameter file (SPFILE) in a platform-specific default location. If you have not created a server parameter file, or if you wish to use a traditional text parameter file instead, you must specify the PFILE clause of the STARTUP command to identify the initialization parameter file.
In the platform-specific default location, Oracle Database locates your initialization parameter file by examining filenames in the following order:
You can direct the database to read initialization parameters from a traditional text initialization parameter file, by using the PFILE clause of the STARTUP command. For example:STARTUP PFILE = /u01/oracle/dbs/init.ora
It is not usually necessary to start an instance with a nondefault server parameter file. However, should such a need arise, you can use this PFILE clause to start an instance with a nondefault server parameter file as follows:
For example, create a text initialization parameter file /u01/oracle/dbs/spf_init.ora that contains only the following parameter:SPFILE = /u01/oracle/dbs/test_spfile.ora
The server parameter file must reside on the machine running the database server.Therefore, the preceding method also provides a means for a client machine to start a database that uses a server parameter file. It also eliminates the need for a client machine to maintain a client-side initialization parameter file. When the client machine reads the initialization parameter file containing the SPFILE parameter, it passes the value to the server where the specified server parameter file is read.
You can start an instance in various modes:
In addition, you can force the instance to start, or start the instance and have complete media recovery begin immediately. The STARTUP command clauses that you specify to achieve these states are illustrated in the following section.
Starting an Instance: Scenarios
The following scenarios describe and illustrate the various states in which you can start up an instance. Some restrictions apply when combining clauses of the STARTUP command.
Starting an Instance, and Mounting and Opening a Database
Normal database operation means that an instance is started and the database is mounted and open. This mode allows any valid user to connect to the database and perform typical data access operations.
Start an instance, read the initialization parameters from the default server parameter file location, and then mount and open the database by using the STARTUP command by itself (you can, of course, optionally specify the PFILE clause):STARTUP
Starting an Instance Without Mounting a Database
You can start an instance without mounting a database. Typically, you do so only during database creation. Use the STARTUP command with the NOMOUNT clause:STARTUP NOMOUNT
Starting an Instance and Mounting a Database
You can start an instance and mount a database without opening it, allowing you to perform specific maintenance operations. For example, the database must be mounted but not open during the following tasks:
Start an instance and mount the database, but leave it closed by using the STARTUP command with the MOUNT clause:STARTUP MOUNT
Restricting Access to an Instance at Startup
You can start an instance, and optionally mount and open a database, in restricted mode so that the instance is available only to administrative personnel (not general database users). Use this mode of instance startup when you need to accomplish one of the following tasks:
Typically, all users with the CREATE SESSION system privilege can connect to an open database. Opening a database in restricted mode allows database access only to users with both the CREATE SESSION and RESTRICTED SESSION system privilege. Only database administrators should have the RESTRICTED SESSION system privilege. Further, when the instance is in restricted mode, a database administrator cannot access the instance remotely through an Oracle Net listener, but can only access the instance locally from the machine that the instance is running on.
Start an instance (and, optionally, mount and open the database)in restricted mode by using the STARTUP command with the RESTRICT clause:STARTUP RESTRICT
Later, use the ALTER SYSTEM statement to disable the RESTRICTED SESSION feature:ALTER SYSTEM DISABLE RESTRICTED SESSION;
If you open the database in nonrestricted mode and later find you need to restrict access, you can use the ALTER SYSTEM statement to do so
Forcing an Instance to Start
In unusual circumstances, you might experience problems when attempting to start a database instance. You should not force a database to start unless you are faced with the following:
If one of these situations arises, you can usually solve the problem by starting a new instance (and optionally mounting and opening the database) using the STARTUP command with the FORCE clause:STARTUP FORCE
If an instance is running, STARTUP FORCE shuts it down with mode ABORT before restarting it.
Starting an Instance, Mounting a Database, and Starting Complete Media Recovery
If you know that media recovery is required, you can start an instance, mount a database to the instance, and have the recovery process automatically start by using the STARTUP command with the RECOVER clause:STARTUP OPEN RECOVER
If you attempt to perform recovery when no recovery is required, Oracle Database issues an error message.
Automatic Database Startup at Operating System Start
Many sites use procedures to enable automatic startup of one or more Oracle Database instances and databases immediately following a system start. The procedures for performing this task are specific to each operating system.
Starting Remote Instances
If your local Oracle Database server is part of a distributed database, you might want to start a remote instance and database. Procedures for starting and stopping remote instances vary widely depending on communication protocol and operating system.
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Oracle 10g Tutorial
Overview Of Administering An Oracle Database
Creating An Oracle Database
Starting Up And Shutting Down
Managing Oracle Database Processes
Managing Control Files
Managing The Redo Log
Managing Archived Redo Logs
Managing Datafiles And Tempfiles
Managing The Undo Tablespace
Using Oracle-managed Files
Using Automatic Storage Management
Managing Space For Schema Objects
Managing Partitioned Tables And Indexes
Managing Hash Clusters
Managing Views, Sequences, And Synonyms
General Management Of Schema Objects
Detecting And Repairing Data Block Corruption
Managing Users And Securing The Database
Managing Automatic System Tasks Using The Maintenance Window
Using The Database Resource Manager
Moving From Dbms_job To Dbms_scheduler
Overview Of Scheduler Concepts
Using The Scheduler
Administering The Scheduler
Distributed Database Concepts
Managing A Distributed Database
Developing Applications For A Distributed Database System
Distributed Transactions Concepts
Managing Distributed Transactions
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