oracle connection number modification

Oracle database is a high-performance, high-availability relational database system that is widely used in enterprise-level applications. When using Oracle database, we may encounter the problem of too many connections, which requires corresponding modification of the number of connections. In this article, we will introduce how to modify the number of connections to the Oracle database.

1. What is Oracle connection number

In Oracle database, the number of connections refers to the number of sessions established to connect to the database. Whenever an application connects to a database through a database client driver, a new session is established. If the concurrency of the application is relatively high, a large number of sessions will be generated, resulting in an increase in the number of connections.

The default maximum number of connections for Oracle database is 150. If the number of connections exceeds this limit, new connection requests will not be processed, causing the application to fail to access the database.

2. Diagnose the problem of too many Oracle connections

When an application accesses the Oracle database, if it is found that the access speed becomes slow or the database cannot be connected, it may be caused by too many connections. . At this time, we can diagnose through the following methods:

1. View the database process

Through the following command, you can view the process information of the database running:

ps -ef |grep ora_ | grep -v grep

If found If there are a large number of processes running, it may be caused by too many connections.

2. View database log

By viewing the log information of the database, you can monitor and diagnose excessive connections, for example:

select * from v$session where status='ACTIVE';

This command can query the current All session information for executing tasks.

SELECT count(*) FROM v$session;

This command can query the number of sessions currently connected to the database.

SELECT * FROM v$resource_limit WHERE resource_name = 'processes';

This command can query the limit of the number of processes and the current usage.

3. Modify the number of Oracle connections

After diagnosing the problem of too many database connections, we need to modify the number of connections to the Oracle database. Modifying the number of Oracle database connections requires configuring multiple parameters. The specific steps are as follows:

1. View the current connection number parameters

Use the following command to view the settings of the current connection number parameters:

SHOW PARAMETER PROCESSES

This command will output the currently set maximum number of processes.

2. Modify the number of connection parameters

To modify the number of connections to the Oracle database, you need to modify the values ​​of relevant parameters. It can be modified in the following three ways:

(1) Modify spfile parameters

Use the following command to modify spfile parameters:

ALTER SYSTEM SET processes=200 SCOPE=SPFILE;

This command will modify the maximum number of processes is 200, and save the changes to the spfile parameter file.

(2) Modify pfile parameters

Use the following command to modify pfile parameters:

ALTER SYSTEM SET processes=200 SCOPE=MEMORY;

This command will modify the maximum number of processes to 200 and save the modification to pfile in the parameter file.

(3) Dynamically modify parameters

Use the following command to dynamically modify the number of database connection parameters:

ALTER SYSTEM SET processes=200;

This command will modify the current maximum number of processes to 200.

3. Restart the database instance

After modifying the connection number parameters, you need to restart the database instance to make the connection number parameters take effect. You can use the following command to restart the database instance:

SHUTDOWN IMMEDIATE;
STARTUP;

This command will shut down the database instance and restart it.

4. Notes

When modifying the connection number parameters of the Oracle database, you need to pay attention to the following points:

1. The number of connections must be moderate

Increasing the maximum number of processes will occupy more memory resources and increase the burden on the system. Therefore, the number of database connections must be reasonably set based on actual business needs and system load.

2. Use pfile parameter file with caution

If you use pfile parameter file for parameter setting, you need to modify the file manually. Therefore, if you need to modify parameters multiple times, it is recommended to use spfile parameter files.

3. Restrictions on dynamically modifying parameters

When dynamically modifying the number of connection parameters, the instance must be restarted immediately after modification, otherwise the parameters will not take effect.

In short, the number of connections to the Oracle database is a very important parameter and has an important impact on the performance and stability of the entire database. Therefore, you must consider carefully when modifying the connection number parameters.

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