DB instance open close-up explanation

Several ways to start the Oracle database shutdown

Several ways to start and shut down Oracle databases

There are several ways to start:
1, Startup Nomount
Non-installation boot, this way startup executable: Rebuild the control file, rebuild the database

Read the Init.ora file and start instance, which starts the SGA and background process, which requires only init.ora files.

2. Startup Mount DBName
Installation starts, this way starts under executable:
Database log archiving,
Database Media Recovery,
Bring the data file online or offline,
Relocate the data file, redo the log file.

Execute "nomount", then open the control file, confirm the location of the data file and the online log file,
However, the data files and log files are not checked for validation at this time.

3. Startup Open dbname
Execute "nomount" first, then execute "Mount", and then open all the database files including the redo log file,
This way you can access the data in the database.

4, startup, equal to the following three commands
Startup Nomount
ALTER DATABASE Mount
ALTER DATABASE Open

5, startup restrict
Constrained mode start
This way the database can be started, but only users with certain privileges are allowed access
When a non-privileged user accesses, the following prompt appears:
ERROR:
Ora-01035:oracle only allow users with RESTRICTED SESSION permissions to use

6. Startup force
Forced start mode
When the database cannot be closed, you can use startup force to complete the shutdown of the database
Close the database first and then execute the normal startup database command

7. Startup pfile= parameter file name
Start mode with initialization parameter file
Read the parameter file first, and then start the database by setting it in the parameter file
Example: Startup Pfile=e:\oracle\admin\oradb\pfile\init.ora

8, startup EXCLUSIVE

There are three ways to switch off:
1. Shutdown normal
Shut down the database in the normal way.

2, Shutdown immediate
Close the database immediately.
Shutdown immediate is executed in SVRMGRL and the database is not shut down immediately.
Instead of shutting down (terminating the session, freeing the session resource) after Oracle performs some cleanup work,
When you cannot close a database by using shutdown, shutdown immediate can complete the operation of the database shutdown.

3, Shutdown abort
Directly shuts down the database, and the session that is accessing the database is suddenly terminated.
If a large number of operations are executing in the database, it takes a long time to restart the database after shutdown abort is executed.

The Oracle database provides several different ways to start and shut down the database, and this article details the differences between these startup and shutdown methods and their different capabilities.

First, start and close the Oracle database
For most Oracle DBAs, the most common way to start and shut down an Oracle database is in the command-line mode of server Manager. From Oracle 8i, the system centralizes all the functions of Server Manager to

Sql*plus, which means that starting and shutting down the database from 8i can be done directly through sql*plus, without the need for Server Manager, but the system still retains the Server Manager in order to remain backwards compatible

Tools. In addition, the graphical user tool (GUI) of Oracle Enterprise Manager can be used to complete the system startup and shutdown, the graphical user interface instance Manager is very simple, not detailed here.

To start and shut down a database, you must log in as a user with Oracle Administrator privileges, typically logged in as a user with SYSDBA permissions. In general, we often use internal users to start and close the database (internal

User is actually a synonym for SYS users to SYSDBA connections). The new version of the Oracle database will phase out internal this internal user, so we'd better set the DBA user to have SYSDBA permissions.

Second, the database startup (startup)
Starting a database requires three steps:

1. Create an Oracle instance (non-installation phase)

2. Install the database by instance (Installation phase)

3. Open the database (open stage)

In the startup command, different options are available to control the different startup steps of the database.

1, STARTUP Nomount

The Nonount option simply creates an Oracle instance. Reads the Init.ora initialization parameter file, initiates a background process, initializes the system global Zone (SGA). The Init.ora file defines the configuration of the instance, including the size of the memory structure and

The number and type of background processes started. The instance name is set according to Oracle_sid and does not have to be the same as the open database name. When the instance is open, the system displays a list of the structure and size of the SGA memory as follows:

Sql> Startup Nomount
The ORACLE routine has been started.
Total System Global area 35431692 bytes
Fixed Size 70924 bytes
Variable Size 18505728 bytes
Database buffers 16777216 bytes
Redo buffers 77824 bytes

2. STARTUP MOUNT

The command creates an instance and installs the database, but does not open the database. The Oracle system reads the contents of the control file about the data file and the redo log file, but does not open the file. This open mode is often used in database maintenance

such as renaming the data file, changing the redo log, and opening the archive. In this open mode, in addition to the list of SGA systems can be seen, the system also gives the \ "database load complete \" prompt.

3. STARTUP

This command completes all three steps to create an instance, install an instance, and open a database. At this point the database makes the data files and redo log files online, and typically requests one or more rollback segments. In addition to the system can see the front

All the prompts in the face startup Mount mode will also give a "database already open \" prompt. At this point, the database system is in a normal working state and can accept user requests.

The ALTER DATABASE command must be used to perform an open database operation if the Open command is opened using the startup Nomount or startup Mount. For example, if you open the number with the startup Nomount mode

The instance was created, but the database was not installed and opened. This is required to run the following two commands for the database to start correctly.

ALTER DATABASE MOUNT;
ALTER DATABASE OPEN;

If you start the database with startup mount, you can open the database by running the following command:

ALTER DATABASE OPEN.

4. Other Open mode

In addition to the three types of database open options described earlier, there are other options.

(1) STARTUP RESTRICT

In this way, the database will be opened successfully, but only some privileged users (users with DBA roles) can use the database. This approach is commonly used to maintain databases, such as data import/export operations

Other users are connected to the database operation data.

(2) STARTUP force

This command is actually a synthesis of forcibly shutting down the database (shutdown abort) and starting the database (startup) two commands. This command is only used when the database is closed and the database is not closed.

(3) ALTER DATABASE OPEN READ only;

This command opens the database as read-only after the instance is created and the database is installed. A product database that only provides query functionality can be opened in this way.

This article is from the starting point network: http://www.nihaoo.com/html/sjk/Oracle/2009/0506/5555.html

The DB instance is turned off in detail