NDB Cluster Configuration Files Multiple Transporters NodeGroupTransporters Beginning with version 8.0.20,  NDB  allocates multiple transporters for communication between pairs of data nodes. The number of transporters so allocated can be influenced by setting an appropriate value for the NodeGroupTransporters  parameter introduced in that release. The original intended use for this parameter was to facilitate upgrades and especially downgrades to and from very old releases with differing default hash map sizes. This is not an issue when upgrading from NDB Cluster 7.3 (or later) to later versions. Setting  NodeGroupTransporters  to a number greater than the number of LDM threads or the number of TC threads, whichever is higher, causes  NDB  to use the maximum of these two numbers of threads. This means that a value greater than this is effectively ignored. This parameter determines the number of transporters used between nodes in the same node group. The default value (0) means that the number of transporters used is the same as the number of LDMs in the node. This should be sufficient for most use cases; thus it should seldom be necessary to change this value from its default. Hash Map Size DefaultHashMapSize Decreasing this parameter online after any tables have been created or modified with DefaultHashMapSize  equal to 3840 is not currently supported. • FragmentLogFileSize Logging and checkpointing.   The following  [ndbd]  parameters control log and checkpoint behavior. Version (or later) NDB 8.0.13 Type or units bytes Default 16M Range 4M - 1G Restart Type IN (NDB 8.0.13) 4089 Version (or later) NDB 8.0.13 Type or units LDM threads Default 240 Range 0 - 3840 Restart Type N (NDB 8.0.13) Version (or later) NDB 8.0.20 Type or units integer Default 0 Range 0 - 32 Added NDB 8.0.20 Restart Type N (NDB 8.0.13)