NDB Cluster Configuration Files applications using the cluster. In any case, performing a few large transactions holds no advantage over using many smaller ones, for the following reasons: The default value for  DataMemory  in NDB 8.0 is 98MB. The minimum value is 1MB. There is no maximum size, but in reality the maximum size has to be adapted so that the process does not start swapping when the limit is reached. This limit is determined by the amount of physical RAM available on the machine and by the amount of memory that the operating system may commit to any one process. 32-bit operating systems are generally limited to 2 − 4GB per process; 64-bit operating systems can use more. For large databases, it may be preferable to use a 64-bit operating system for this reason. The  IndexMemory  parameter is deprecated (and subject to future removal); any memory assigned to IndexMemory  is allocated instead to the same pool as  DataMemory , which is solely responsible for all resources needed for storing data and indexes in memory. In NDB 8.0, the use of  IndexMemory  in the cluster configuration file triggers a warning from the management server. You can estimate the size of a hash index using this formula: fragments  is the number of fragments,  fragment_replicas  is the number of fragment replicas (normally 2), and  rows  is the number of rows. If a table has one million rows, eight fragments, and two fragment replicas, the expected index memory usage is calculated as shown here: Index statistics for ordered indexes (when these are enabled) are stored in the mysql.ndb_index_stat_sample  table. Since this table has a hash index, this adds to index memory usage. An upper bound to the number of rows for a given ordered index can be calculated as follows: •Large transactions are not any faster than smaller ones •Large transactions increase the number of operations that are lost and must be repeated in event of transaction failure •Large transactions use more memory • IndexMemory size = ( ( fragments  * 32K) + ( rows  * 18) ) *  fragment_replicas ((8 * 32K) + (1000000 * 18)) * 2 = ((8 * 32768) + (1000000 * 18)) * 2 = (262144 + 18000000) * 2 = 18262144 * 2 = 36524288 bytes = ~35MB sample_size= key_size + ((key_attributes + 1) * 4) sample_rows = IndexStatSaveSize * ((0.01 * IndexStatSaveScale * log$_{2}$(rows * sample_size)) + 1) 4076 Version (or later) NDB 8.0.13 Type or units bytes Default 0 Range 1M - 1T Deprecated Yes (in NDB 7.6) Restart Type N (NDB 8.0.13)