NDB Cluster Configuration Files Restart Type N (NDB 8.0.13) The memory affected by this parameter is used for tracking operations fired when updating index tables and reading unique indexes. This memory is used to store the key and column information for these operations. It is only very rarely that the value for this parameter needs to be altered from the default. The default value for  TransactionBufferMemory  is 1MB. Normal read and write operations use a similar buffer, whose usage is even more short-lived. The compile-time parameter  ZATTRBUF_FILESIZE  (found in  ndb/src/kernel/blocks/Dbtc/ Dbtc.hpp ) set to 4000 × 128 bytes (500KB). A similar buffer for key information,  ZDATABUF_FILESIZE (also in  Dbtc.hpp ) contains 4000 × 16 = 62.5KB of buffer space.  Dbtc  is the module that handles transaction coordination. Transaction resource allocation parameters.   The parameters in the following list are used to allocate transaction resources in the transaction coordinator ( DBTC ). Leaving any one of these set to the default (0) dedicates transaction memory for 25% of estimated total data node usage for the corresponding resource. The actual maximum possible values for these parameters are typically limited by the amount of memory available to the data node; setting them has no impact on the total amount of memory allocated to the data node. In addition, you should keep in mind that they control numbers of reserved internal records for the data node independent of any settings for  MaxDMLOperationsPerTransaction , MaxNoOfConcurrentIndexOperations ,  MaxNoOfConcurrentOperations , MaxNoOfConcurrentScans ,  MaxNoOfConcurrentTransactions ,  MaxNoOfFiredTriggers , MaxNoOfLocalScans , or  TransactionBufferMemory  (see Transaction parameters and Transaction temporary storage). • ReservedConcurrentIndexOperations Version (or later) NDB 8.0.16 Type or units numeric Default 0 Range 0 - 4294967039 (0xFFFFFEFF) Added NDB 8.0.16 Restart Type N (NDB 8.0.13) Number of simultaneous index operations having dedicated resources on one data node. • ReservedConcurrentOperations Version (or later) NDB 8.0.16 Type or units numeric Default 0 Range 0 - 4294967039 (0xFFFFFEFF) Added NDB 8.0.16 Restart Type N (NDB 8.0.13) Number of simultaneous operations having dedicated resources in transaction coordinators on one data node. • ReservedConcurrentScans 4083