oracle startup shutdown

Oracle is a powerful database management system that is widely used in enterprise-level applications. When using Oracle, starting and shutting down a database instance are very important operations.

Start the Oracle database instance

To start the Oracle database instance, you need to first understand the Oracle startup process. The Oracle database startup process mainly consists of three stages: Nomount, Mount and Opened. The specific meanings of these three stages are as follows:

1. Nomount

The Nomount stage indicates that the Oracle instance has been started, but the database has not yet been mounted. At this stage, the Oracle instance only provides basic functions of startup and connection management.

2. Mount

The Mount stage indicates that the database has been mounted to the Oracle instance. During this stage, an association is established between the Oracle instance and the database, and various background processes begin to be started.

3. Opened

The Opened stage indicates that the Oracle database has been fully started and is in normal operation.

After understanding the Oracle startup process, we can start the Oracle database instance as needed. The following are the steps to start an Oracle instance:

1. Use an Oracle administrator account (such as sys or system) to connect to the database

$ sqlplus /nolog
SQL> connect / as sysdba

2. Start Oracle instance

SQL> startup

3. Confirm the startup status of Oracle instance

SQL> select status from v$instance;

At this time, "OPEN" should be output to indicate that the Oracle instance is already in the Opened stage.

Close the Oracle database instance

Oracle also needs to pay attention to some things when closing the database instance. Before shutting down the Oracle instance, make sure that all users have disconnected from the Oracle database, otherwise data loss may occur.

The following are the steps to shut down an Oracle instance:

1. Disconnect all users from the database

SQL> alter system enable restricted session;
SQL> shutdown immediate;

2. Confirm the shutdown status of the Oracle instance again

SQL> select status from v$instance;

At this time, it should The output "CLOSED" indicates that the Oracle instance has been closed.

Summary

Starting and shutting down an Oracle database instance is an important operation in Oracle database management. Pay attention to the following matters:

1. The process of starting an Oracle instance usually includes three steps: stages: Nomount, Mount and Opened.
2. Before starting the Oracle instance and shutting down the Oracle instance, make sure that all users have disconnected from the Oracle database.
3. The process of shutting down an Oracle instance is opposite to the process of starting an Oracle instance. First disconnect all users and then shut down the instance.

Through the above operations, you can successfully start and shut down the Oracle database instance to ensure the normal operation of the Oracle database.

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