Let's talk about PGA modifications in Oracle database management

Oracle database is an extremely powerful relational database management system. In the management of Oracle database, PGA (Program Global Area) is an important concept. The PGA can be thought of as a pool of memory used by all individual processes to perform operations such as SQL code, sorting, hashing, and joining. Due to the importance of PGA, administrators need to pay attention to PGA size and its optimization. If you need to modify the PGA of your Oracle database, this process should be done with caution. In the next article, we will introduce the specific steps to modify the Oracle database PGA.

Understand the size of the PGA

Before trying to modify the PGA of the Oracle database, you need to first understand the size of the PGA already used by your Oracle database. The interactive command to query the PGA size is v$pgastat. By executing the following SQL statement, you can obtain the PGA size:

select sum(value)/(1024*1024) "PGA Size in MB" from v$ pgastat where name like '%aggregate PGA target parameter%';

The above SQL query will display the size of the PGA that has been used by the Oracle database, usually hundreds of megabytes to several G. You can resize the PGA as needed.

PGA modification steps

The following are the specific steps to modify the Oracle database PGA:

1. Determine the instance of PGA that needs to be modified.

Normally, the PGA size should be set to a fixed value on the host. You need to identify the instance where the PGA needs to be modified. You can list the Oracle instance with the following command:

ps –ef | grep pmon

2. Determine the PGA value.

Before modifying the PGA, you need to determine the value you want to set for the PGA. You can refer to the above SQL query to obtain the already used PGA size and determine the new PGA size based on visual guessing and system load.

3. Formally modify the size of PGA.

Use SQL commands or dbca to modify PGA. Before modifying the PGA, make sure you have backed up important data in the repository. Two common methods for modifying the PGA size are provided below:

Modify the PGA through SQL commands:

alter system set pga_aggregate_target=1500m scope=both;

In this command , we adjust the PG to 1.5 G, this command will permanently change the PGA.

Modify PGA through Oracle Database Configuration Assistant:

You can also use Oracle Database Configuration Assistant to modify the PGA size. In the Oracle Database Configuration Assistant, select the "Modify Database" option and then select the "Modify Memory Parameters" option to modify the PGA.

Summary

The above are the steps to modify the PGA size of the Oracle database. When running a production application, it is important to note that data is saved in a database and errors in migrating or changing the data may result in data loss. Before modifying PGA, make sure you back up important data and back up your database. If you have any problems modifying the PGA size, please seek help from Oracle's official documentation and the Oracle Database Community. Remember, any database modification needs to be tested multiple times to ensure that it does not negatively impact the security and performance of the database.

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