The difference between Startup,startup Mount,startup Nomount

Original address: http://www.blogjava.net/freeman1984/archive/2011/05/17/350373.html

Startup Nomount option: (read initialization parameter file, start instance)
The startup Nomount option launches the instance, but does not install the database. When the database is started in this mode, the parameter files are read, the background processes and memory structures are started, but they are not attached or communicated to the disk structure of the database. When the instance is in this state, the database is not available.


STARTUP mount option: (Open control file)
The Startup Mount option performs all the work of the startup Nomount option, but additionally attaches the database structure and interacts with those structures. Oracle then obtains information from the control files it uses to locate and attach to the primary database structure. When you are in this mode, you can perform some administrative tasks, such as recovery.


STARTUP Open option: (Open data file, log file)
If no mode is specified on the startup command line, the startup Open option is the default startup mode. The startup Open option performs all the steps for the startup Nomount and startup Mount options. This option turns the database to be available to all users.


STARTUP Force option:
You can use the Startup force option if you are having trouble starting the database in the normal way. The Startup force option first closes the database unexpectedly and then restarts it.


STARTUP Restrict option:
The startup restrict option launches the database and puts it into open mode, but grants access only to users who have restricted session permissions.


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Rman> Startup Nomount
Connected to target database (not started)
Oracle routines Started
System global Zone total 135338868 bytes
Fixed Size 453492 bytes
Variable Size 109051904 bytes
Database buffers 25165824 bytes
Redo buffers 667648 bytes


Rman> Startup Mount
Connected to target database (not started)
Oracle routines Started
The database is loaded
System global Zone total 135338868 bytes
Fixed Size 453492 bytes
Variable Size 109051904 bytes
Database buffers 25165824 bytes
Redo buffers 667648 bytes


Rman> Startup
Connected to target database (not started)
Oracle routines Started
The database is loaded
Database is open
System global Zone total 135338868 bytes
Fixed Size 453492 bytes
Variable Size 109051904 bytes
Database buffers 25165824 bytes
Redo buffers 667648 bytes


Above is three types of screenshots, startup Nomount just started the instance and did not start the database, startup Mount started the instance, and loaded the database, but the database is not open, startup is the most complete, instance, database loading, database open all completed.
For example, the following:


Microsoft Windows XP [version 5.1.2600]
(C) Copyright 1985-2001 Microsoft Corp.


C:\Documents and settings\administrator>cd\


C:\>sqlplus/nolog


Sql*plus:release 9.2.0.1.0-production on Monday September 21 15:21:50 2009


Copyright (c) 1982, 2002, Oracle Corporation. All rights reserved.


Sql> connect/@dwj as Sysdba
is connected.
Sql> Startup Nomount
ORA-01081: Unable to start an ORACLE---that is already running please close first
sql> Shutdown Abort
The ORACLE routine has been closed.
Sql> Startup Nomount
The ORACLE routine has started.


Total System Global area 135338868 bytes
Fixed Size 453492 bytes
Variable Size 109051904 bytes
Database buffers 25165824 bytes
Redo buffers 667648 bytes
Sql>