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Dropping node groups.  The ndb_mgm  client supports a DROP NODEGROUP  command, but it is possible to drop a node group only when no data nodes in the node group contain any data. Since there is currently no way to “empty”  a specific data node or node group, this command works only the following two cases: 

1. After issuing CREATE NODEGROUP  in the ndb_mgm  client, but before issuing any ALTER TABLE ... REORGANIZE PARTITION  statements in the mysql  client. 

2. After dropping all NDBCLUSTER  tables using DROP TABLE . 

TRUNCATE TABLE  does not work for this purpose because the data nodes continue to store the table definitions. 

## 23.5.7.2 Adding NDB Cluster Data Nodes Online: Basic procedure 

In this section, we list the basic steps required to add new data nodes to an NDB Cluster. This procedure applies whether you are using ndbd  or ndbmtd  binaries for the data node processes. For a more detailed example, see Section 23.5.7.3, “Adding NDB Cluster Data Nodes Online: Detailed Example” . 

Assuming that you already have a running NDB Cluster, adding data nodes online requires the following steps: 

1. Edit the cluster configuration config.ini  file, adding new [ndbd]  sections corresponding to the nodes to be added. In the case where the cluster uses multiple management servers, these changes need to be made to all config.ini  files used by the management servers. 

You must be careful that node IDs for any new data nodes added in the config.ini  file do not overlap node IDs used by existing nodes. In the event that you have API nodes using dynamically allocated node IDs and these IDs match node IDs that you want to use for new data nodes, it is possible to force any such API nodes to “migrate” , as described later in this procedure. 

2. Perform a rolling restart of all NDB Cluster management servers. 

