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3. Setting ndb_data_node_neighbour  further decreases the effective Group  value by 50, causing this node to be regarded as the nearest node. This is needed only when all data nodes are on hosts other than that hosts the API node and it is desirable to dedicate one of them to the API node. In normal cases, the default adjustment described previously is sufficient. 

Frequent changes in ndb_data_node_neighbour  are not advisable, since this changes the state of the cluster connection and thus may disrupt the selection algorithm for new transactions from each thread until it stablilizes. 

• ndb_read_backup 

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Enable read from any fragment replica for any NDB  table subsequently created; doing so greatly improves the table read performance at a relatively small cost to writes. 

To enable or disable read from any fragment replica for an individual table, you can set the NDB_TABLE option READ_BACKUP  for the table accordingly, in a CREATE TABLE  or ALTER TABLE  statement; see Section 13.1.20.11, “Setting NDB_TABLE Options” , for more information. 

• ndb_recv_thread_activation_threshold 

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When this number of concurrently active threads is reached, the receive thread takes over polling of the cluster connection. 

This variable is global in scope. It can also be set at startup. 

• ndb_recv_thread_cpu_mask 

Command-Line Format --ndb-recv-thread-cpu-mask=mask 

