How to uninstalling a SQL Server Clustered Instance
Step- by -Step process :-
Uninstalling a clustered instance of SQL Server 2008 R2 is actually an easy thing to do. It might be intimidating for your first attempt so I would highly recommend doing this first on a non-production cluster (Passive Node)
Step 1: Login into the non-active node for the SQL Server clustered instance that needs to be uninstalled. This instance might be an active node for another instance of SQL Server and this is fine.
Step 2: Start the SQL 2008 R2 installer Set up file with run as administrator and go to Maintenance section and select remove node from a SQL Server failover cluster. as shown below screen
Step 3: Go through the setup support rules and click ok.
Step 4: Go through next screen of setup support rules and click next. If you don't see "Passed" for all items address this issue before going forward.
Step 5: Select the clustered instance you want to uninstall. Notice that we will uninstall the SQLxxx instance which has two clustered nodes AAAA and BBBB. This is an active -active cluster and we will are starting with the passive node AAAA.
Step 6: Verify that all components you want to remove are selected. Click on the remove button to start the process to remove the SQL Server clustered instance on this node.
Step 7: It is will take some time to uninstall the SQLxx instance on clustered node.
Step 8: Uninstall is complete on this node. Congratulations you just uninstalled SQL Server node. Now it's time to uninstall the other nodes use by the SQL Server Clustered instance.
Step 9: Repeat steps 1 to 8 on active node used for the SQL Server clustered instance. Make sure you uninstall the active node last.
Note: when you repeat step 5 you should notice that the previous uninstalled node is not listed under nodes.
