Use  to decommission a DataNode component.
- 
            Using Ambari Web, browse the Hosts
               page. 
         
- 
            Find and click the FQDN of the host on which the DataNode component resides.
         
- 
            Using the Actions control, click .
            
            The UI shows Decommissioning status while in process. 
When this DataNode decommissioning process is finished, the
         Action option shows Recommission.
