oracle delete instance

Oracle is a very popular relational database management system. When using Oracle, sometimes you need to delete an instance (instance), for example, because you want to rebuild a new instance or because you need to clear old data. This article will introduce how to delete an Oracle instance.

First, we need to confirm the status of the current instance. You can check using the following command:

$ ps -ef | grep pmon

If the instance is running, one or more processes will be output immediately following it, as shown below:

oracle   1234     1  0 09:06 ?        00:00:00 ora_pmon_MYINSTANCE

Where "MYINSTANCE" is the name of the instance .

If the instance is running, we need to stop the instance first. You can use the following command to stop:

$ sqlplus '/as sysdba'
SQL> shutdown immediate;

This command will immediately close the database and stop the instance.

Next, we need to confirm some instance information. You can use the following command to view the directory structure of the instance:

$ ls $ORACLE_HOME/dbs/myinstance*

If there are one or more files related to the instance, such as "myinstance.ora", "myinstance.pfile", etc., you need to ensure that these files will be deleted .

In addition, we also need to delete the configuration of the instance in Oracle Net Listener. This can be confirmed using the following command:

$ lsnrctl status LISTENER

where LISTENER is the name of the Oracle Net Listener. The output result will contain some content as shown below:

(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=myhost)(PORT=1521)))
SERVICE_LISTENER =
  (DESCRIPTION=
    (ADDRESS=(PROTOCOL=TCP)(HOST=myhost)(PORT=1521))
    (ADDRESS=(PROTOCOL=IPC)(KEY=EXTPROC1521))
  )
SID_LIST_LISTENER =
  (SID_LIST=
    (SID_DESC=
      (GLOBAL_DBNAME=myinstance)
      (ORACLE_HOME=/usr/local/oracle)
      (SID_NAME=myinstance)
    )
  )

where, myhost is the host name of the Oracle server, 1521 is the port number used by Oracle Net Listener, and myinstance is the name of the instance. All references to instances need to be deleted.

You can use the following command to delete the configuration in Oracle Net Listener:

$ lsnrctl stop LISTENER
$ vi $ORACLE_HOME/network/admin/listener.ora
$ vi $ORACLE_HOME/network/admin/tnsnames.ora
$ lsnrctl start LISTENER

Among them, LISTENER is the name of Oracle Net Listener, $ORACLE_HOME/network/admin/listener.ora is the name of Oracle Net Listener Configuration file, $ORACLE_HOME/network/admin/tnsnames.ora is the configuration file used by the Oracle client. All content related to the instance needs to be deleted in these two files.

Finally, we need to delete the archive directory and data files of the instance. You can use a command similar to the following to confirm:

$ ls /u01/app/oracle/oradata/myinstance/

Then you can use the following command to delete these data files:

$ rm -rf /u01/app/oracle/oradata/myinstance/

Finally, we also need to delete the init.ora file and Oracle's environment variable settings. You can use the following command to delete the init.ora file:

$ rm $ORACLE_HOME/dbs/myinstance.ora
$ rm $ORACLE_HOME/dbs/myinstance.pfile

Then you can use a command similar to the following to delete Oracle's environment variable settings:

$ unset ORACLE_HOME
$ unset ORACLE_SID

The above are all the steps to delete the Oracle instance. It should be noted that before performing these steps, you need to make adequate backups to avoid data loss due to misoperation.

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