oracle delete connection

Oracle database is a very popular relational database management system. It has powerful data processing capabilities and is widely used in all walks of life. In the process of database operation and maintenance management, deleting connections is one of the tasks that often requires operations. In this article, we will explain in detail how to delete a connection in Oracle database.

1. What is a connection

In Oracle database, connection refers to the communication channel between the client application and Oracle database. Applications access the database through connections and perform SQL queries and update operations. Connections can be opened by multiple client applications simultaneously, but a connection can only be used by one user session.

There are two types of connections in Oracle database: physical connections and logical connections. Physical connection refers to the physical communication connection between the client application and the database server. Logical connections are logical communication connections between applications and databases, which are implemented based on physical connections.

2. Reasons for deleting connections

In Oracle database operation and maintenance management, it is necessary to frequently clean up connections that are no longer used. This is mainly for the following reasons:

1. Release database resources

When the database is running, connections will occupy a large amount of system resources, such as memory, CPU and network bandwidth. If the connection is not closed or cleaned up in time, database resources will be occupied for a long time, thus affecting the performance and stability of the system.

2. Avoid occupying database locks

In Oracle database, when a connection accesses a transaction, the database resources and locks related to the transaction will be occupied. If the connection is not closed, these resources and locks will continue to be occupied, causing other connections to be unable to access these resources and locks, resulting in business anomalies.

3. Security considerations

In order to protect the security of the database, some connections require security measures, such as authentication, encryption, etc. If the connection is not closed or cleaned up in time, the security of the database may be affected.

3. Methods of deleting connections

There are many ways to delete connections. Below we will introduce some of the commonly used ones.

1. Use Oracle Enterprise Manager to manage connections

Oracle Enterprise Manager is one of the Oracle database management tools, which can manage databases and connections through a graphical interface. In Enterprise Manager, you can view all current connections, including physical connections and logical connections, as well as connection-related information, such as connection ID, user name, IP address, session status, etc.

To delete a connection, you first need to log in to the Enterprise Manager management interface and find the connection management module. Then select the connection you want to delete and click the "Disconnect" button. The system will confirm whether to disconnect the connection. After confirmation, the connection will be disconnected immediately and related resources and locks will be released.

2. Use SQL statements to manage connections

In addition to using Oracle Enterprise Manager, we can also use SQL statements to manage connections. Oracle Database provides several packages and views for querying and managing connections. Below we will introduce several commonly used packages and views.

① v$session view

v$session view is an important system dynamic performance view that can be used to query all current connections. When querying the v$session view, you can use the following SQL statement:

SELECT sid,serial#,username,program,sql_id,logon_time,status
FROM v$session
WHERE username='YOUR_USER_NAME';

where sid is the session ID, serial# is the serial number, username is the connected user name, program is the client application name, sql_id is the currently executed SQL ID, logon_time is the connection time, and status is the session status.

To delete a connection, you can use the following SQL statement:

ALTER SYSTEM KILL SESSION 'sid,serial#';

Where, sid and serial# are the session ID and serial number, which can be obtained by querying the v$session view. After executing the above SQL statement, the system will confirm whether to terminate the connection. After confirmation, the connection will be terminated immediately and related resources and locks will be released.

② dbms_system package

The dbms_system package is one of the system packages of the Oracle database and is used to perform system-level operations, such as closing the database, clearing the cache, etc. In the dbms_system package, there is a KILL_SESSION procedure that can be used to terminate a specified connection. An example of using the KILL_SESSION procedure is as follows:

EXEC dbms_system.kill_session(sid => YOUR_SESSION_ID, serial# => YOUR_SERIAL_NUMBER);

Where YOUR_SESSION_ID and YOUR_SERIAL_NUMBER are the session ID and sequence number of the connection that needs to be terminated, which can be obtained by querying the v$session view.

4. Summary

Deleting connections is an important task in Oracle database operation and maintenance management. It can release database resources, avoid occupying database locks and improve database security. This article describes methods for dropping connections, including using Oracle Enterprise Manager to manage connections and using SQL statements to manage connections. Operation and maintenance personnel can choose a method that suits them according to the actual situation, strengthen the management and maintenance of the database, and improve the performance and stability of the database.

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