Deleting Oracle RAC from a Cluster Node

To remove Oracle Real Application Clusters (Oracle RAC) from a cluster node, you must delete the database instance and the Oracle RAC software before removing the node from the cluster.

Note:

If there are no database instances on the node that you want to delete, then remove Oracle RAC.

Deleting Instances from Administrator-Managed Databases

Deleting an administrator-managed database instance involves using Oracle DBCA to delete the Oracle AI Database instance.

Note:

Before deleting an instance from an Oracle RAC database using SRVCTL, do the following:

If you have services configured, then relocate the services

Modify the services so that each service can run on one of the remaining instances

Ensure that the instance to be removed from an administrator-managed database is neither a preferred nor an available instance of any service

Using Oracle DBCA in Silent Mode to Delete Instances from Nodes

You can use Oracle DBCA in silent mode to delete a database instance from a node.

To remove an instance, use the following command syntax. Provide a node name only if you are deleting an instance from a node other than the one on where Oracle DBCA is running as shown in the following example where password is the SYSDBA password:

dbca -silent -deleteInstance [-nodeName node_name] -gdbName gdb_name
-instanceName instance_name [-sysDBAUserName sysdba] [-sysDBAPassword password]

The following table describes the values that you need to supply for each variable.

Table: Variables in the Oracle DBCA Silent Mode Syntax

Variable	Description
`node_name`	The node on which you want to add (or delete) the instance.
`gdb_name`	Global database name.
`instance_name`	Name of the instance. Provide an instance name only if you want to override the Oracle naming convention for Oracle RAC instance names.
`sysdba`	Name of the Oracle user with `SYSDBA` privileges.
`password`	Password for the `SYSDBA` user.

At this point, you have accomplished the following:

Deregistered the selected instance from its associated Oracle Net Services listeners
Deleted the selected database instance from the instance's configured node
Removed the Oracle Net configuration
Deleted the Oracle Flexible Architecture directory structure from the instance's configured node.

Using Oracle DBCA in Interactive Mode to Delete Instances from Nodes

To delete an Oracle Real Application Clusters (Oracle RAC) instance using Oracle DBCA in interactive mode, complete this procedure.

Verify there is a current backup of OCR.
Run the ocrconfig -showbackup command to ensure there is a valid backup.
Start Oracle DBCA.
Start Oracle DBCA on a node other than the node that hosts the instance that you want to delete. The database and the instance that you plan to delete should continue to be started and running during this step.
On the Oracle DBCA Operations page, select Instance Management, click Next, and Oracle DBCA displays the Instance Management page.
On the Instance Management page, select Delete Instance, click Next, and Oracle DBCA displays the List of Cluster Databases page.
Select an Oracle RAC database from which to delete an instance. Click Next and Oracle DBCA displays the List of Cluster Database Instances page. The List of Cluster Database Instances page shows the instances that are associated with the Oracle RAC database that you selected and the status of each instance.
On the List of Cluster Databases page, select the Oracle RAC database from which to delete the instance, as follows:
1. On the List of Cluster Database Instances page, Oracle DBCA displays the instances that are associated with the Oracle RAC database that you selected and the status of each instance. Select the cluster database from which you will delete the instance. Click Finish.
2. Click OK on the Confirmation dialog to proceed to delete the instance.
3. Click OK on the next Confirmation dialog to delete the instance and related Optimal Flexible Architecture (OFA) directory structure.
  Oracle DBCA displays a progress dialog showing that Oracle DBCA is deleting the instance. During this operation, Oracle DBCA removes the instance and the instance's Oracle Net configuration.
  
  Click No and exit Oracle DBCA or click Yes to perform another operation. If you click Yes, then Oracle DBCA displays the Operations page.
Verify that the dropped instance's redo thread has been removed using SQL*Plus to query the V$LOG view from an existing instance. If the redo thread is not disabled, then disable the thread. For example:
```
SQL> ALTER DATABASE DISABLE THREAD 2;
```
Verify that the instance has been removed from OCR by running the following command, where db_unique_name is the name of the database:
```
srvctl config database -db db_unique_name
```
If you are deleting more than one node, then repeat these steps to delete the instances from all the nodes that you are going to delete.

Removing Oracle RAC

This procedure removes the Oracle RAC software from the node you are deleting from the cluster and updates inventories on the remaining nodes.

If there is a listener in the Oracle RAC home on the node you are deleting, then you must disable and stop it before deleting the Oracle RAC software. Run the following commands on any node in the cluster, specifying the name of the listener and the name of the node you are deleting:
```
C:\srvctl disable listener -listener listener_name -node name_of_node_to_delete
C:\srvctl stop listener -listener listener_name -node name_of_node_to_delete
```
Deinstall the Oracle home from the node that you are deleting by running the following command from the Oracle_home\ deinstall directory:
```
deinstall -local
```

If you have a shared Oracle RAC home, then append the -cfs option to the command example in this step and provide a complete path location for the cluster file system.

Deleting Nodes from the Cluster

After you delete the instance, you can begin the process of deleting the node from the cluster.

To delete a node from the cluster, you run scripts on the node that you want to delete to remove the Oracle Grid Infrastructure installation. You then run scripts on the remaining nodes to update the node list.