oracle instance delete

Oracle is an enterprise-class database management system that can be used to store and manage large amounts of data. In some cases, you may need to remove the Oracle instance, especially when rebuilding the database or reinstalling the Oracle software. This article describes how to delete an Oracle instance and the possible effects of deleting an instance.

Preparation work

Before deleting the Oracle instance, you need to perform the following preparation work:

1. Confirm whether the instance to be deleted is in a stopped state: In Oracle When an instance starts, the database creates a set of processes in memory. Before deleting an instance, you must ensure that the instance is not running. You can check whether the instance is running by executing the following command:

   $ ps -ef | grep ora_pmon_

   If there are any processes containing the "ora_pmon_" keyword in the output, then the instance is running.

2. Backup instance: Before deleting the instance, it is best to back up the database first. This ensures that no data is lost when the instance is deleted. This can be accomplished using Oracle's backup and restore tools.
3. Get administrator privileges: On Linux or Unix systems, deleting an Oracle instance requires administrator privileges. You can switch to the administrator user using the "su" or "sudo" command.

Delete the Oracle instance

After completing the above preparations, you can delete the Oracle instance by following the following steps:

1. Stop the database instance: use " shutdown" command to stop the Oracle instance. To stop all instances, you can execute the following command:

   $ sqlplus / as sysdba
   SQL> shutdown immediate;

   This command may fail if there are other users connecting to the instance. In this case, you can use the "shutdown abort" command to force stop the instance.

2. Remove Oracle instance files: In the Oracle instance directory, there are many files that need to be deleted. For example, Oracle program files, configuration files, data files, log files, etc. The easiest way to delete an Oracle instance is to use the Oracle Universal Installer:

   $ cd /opt/oracle
   $ ./oui

   Oracle Universal Installer will display an interface where you can select the instance to delete. After selecting the instance to be deleted, click the Delete button to delete the instance.

   If you cannot use Oracle Universal Installer to delete the instance, you can also delete the instance files manually. This method requires removing the database and listener configuration first, and then deleting the file.

   $ cd $ORACLE_HOME
   $ dbca -silent -deleteDatabase -sourceDB <DB_SID>
   $ netca -silent -delete -responseFile <LISTENER_NAME>.rsp
   $ cd ..
   $ rm -rf <ORACLE_INSTANCE_DIR>

3. Delete users and groups from the system: After deleting an Oracle instance, created users and groups may be deleted. These users and groups can be deleted by executing the following command:

   $ userdel <ORACLE_USER>
   $ groupdel <ORACLE_GROUP>

   Where is the user created to run the Oracle instance, and is the group to which the user belongs.

Possible Impact

Deleting an Oracle instance may have the following impacts on the system:

1. Data loss: When deleting an instance, if there is no Backing up data or incomplete data backup may result in data loss. Therefore, before deleting an instance, always ensure that the data has been backed up and that the backup is complete.
2. Users connected to the instance are disconnected: Before deleting the instance, you need to ensure that all connections to the instance have been stopped. Otherwise, users already connected to the instance will be forced to disconnect and may lose ongoing work.
3. Affect other instances: If you delete an instance that shares an Oracle installation, other instances may also be affected. Therefore, before deleting an instance, make sure you have checked whether other instances have been stopped.

Conclusion

Before deleting the Oracle instance, you need to ensure that the data has been backed up and the instance has stopped running. You can use Oracle Universal Installer to easily delete instances. If this tool is not available, you can also delete the instance files manually. It should be noted that deleting an instance may cause data loss or affect other instances. Therefore, please consider carefully before deleting an instance.

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