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• --usage 

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Display help text and exit; same as --help. 

• --version 

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Display version information and exit. 

## 23.4.3 ndbmtd — The NDB Cluster Data Node Daemon (Multi-Threaded) 

ndbmtd  is a multithreaded version of ndbd , the process that is used to handle all the data in tables using the NDBCLUSTER  storage engine. ndbmtd  is intended for use on host computers having multiple CPU cores. Except where otherwise noted, ndbmtd  functions in the same way as ndbd ; therefore, in this section, we concentrate on the ways in which ndbmtd  differs from ndbd , and you should consult Section 23.4.1, “ndbd — The NDB Cluster Data Node Daemon” , for additional information about running NDB Cluster data nodes that apply to both the single-threaded and multithreaded versions of the data node process. 

Command-line options and configuration parameters used with ndbd  also apply to ndbmtd . For more information about these options and parameters, see Section 23.4.1, “ndbd — The NDB Cluster Data Node Daemon” , and Section 23.3.3.6, “Defining NDB Cluster Data Nodes” , respectively. 

ndbmtd  is also file system-compatible with ndbd . In other words, a data node running ndbd  can be stopped, the binary replaced with ndbmtd , and then restarted without any loss of data. (However, when doing this, you must make sure that MaxNoOfExecutionThreads  is set to an apppriate value before restarting the node if you wish for ndbmtd  to run in multithreaded fashion.) Similarly, an ndbmtd binary can be replaced with ndbd  simply by stopping the node and then starting ndbd  in place of the multithreaded binary. It is not necessary when switching between the two to start the data node binary using --initial . 

Using ndbmtd  differs from using ndbd  in two key respects: 

1. Because ndbmtd  runs by default in single-threaded mode (that is, it behaves like ndbd ), you must configure it to use multiple threads. This can be done by setting an appropriate value in the config.ini  file for the MaxNoOfExecutionThreads  configuration parameter or the ThreadConfig  configuration parameter. Using MaxNoOfExecutionThreads  is simpler, but ThreadConfig  offers more flexibility. For more information about these configuration parameters and their use, see Multi-Threading Configuration Parameters (ndbmtd). 

2. Trace files are generated by critical errors in ndbmtd  processes in a somewhat different fashion from how these are generated by ndbd  failures. These differences are discussed in more detail in the next few paragraphs. 

Like ndbd , ndbmtd  generates a set of log files which are placed in the directory specified by DataDir  in the config.ini  configuration file. Except for trace files, these are generated in the same way and have the same names as those generated by ndbd . 

In the event of a critical error, ndbmtd  generates trace files describing what happened just prior to the error’ occurrence. These files, which can be found in the data node’s DataDir , are useful for analysis of problems by the NDB Cluster Development and Support teams. One trace file is generated for each ndbmtd  thread. The names of these files have the following pattern: 

