Adding NDB Cluster Data Nodes Online You can use the  ALL STATUS  command in the  ndb_mgm  client to see when the cluster has entered single user mode. You can also check the  status  column of the  ndbinfo.nodes  table (see Section 23.5.14.38, “The ndbinfo nodes Table” , for more information). Example: ndb_mgm>  ENTER SINGLE USER MODE 5 After this command has executed and the cluster has entered single user mode, the API node whose node ID is  5  becomes the cluster’s only permitted user. The node specified in the preceding command must be an API node; attempting to specify any other type of node is rejected. Note When the preceding command is invoked, all transactions running on the designated node are aborted, the connection is closed, and the server must be restarted. The command  EXIT SINGLE USER MODE  changes the state of the cluster’s data nodes from single user mode to normal mode. API nodes—such as MySQL Servers—waiting for a connection (that is, waiting for the cluster to become ready and available), are again permitted to connect. The API node denoted as the single-user node continues to run (if still connected) during and after the state change. There are two recommended ways to handle a node failure when running in single user mode: Example: ndb_mgm>  EXIT SINGLE USER MODE •Method 1: 1. Finish all single user mode transactions 3. Restart the cluster’s data nodes 2. Issue the  EXIT SINGLE USER MODE  command •Method 2: Restart storage nodes prior to entering single user mode. 23.5.7 Adding NDB Cluster Data Nodes Online This section describes how to add NDB Cluster data nodes “online” —that is, without needing to shut down the cluster completely and restart it as part of the process. Important Currently, you must add new data nodes to an NDB Cluster as part of a new node group. In addition, it is not possible to change the number of fragment replicas (or the number of nodes per node group) online. This section provides general information about the behavior of and current limitations in adding NDB Cluster nodes online. 23.5.7.1 Adding NDB Cluster Data Nodes Online: General Issues 4479