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NDBMTD(8)			      MySQL Database System				NDBMTD(8)

NAME
       ndbmtd - the MySQL Cluster data node daemon (multi-threaded version)

SYNOPSIS
       ndbmtd options

DESCRIPTION
       ndbmtd is a multi-threaded 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 ndbd(8), for additional information about
       running MySQL Cluster data nodes that apply to both the single-threaded and multi-threaded
       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 ndbd(8), and Section 17.3.2.6,
       "Defining MySQL 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
       multi-threaded fashion.) Similarly, an ndbmtd binary can be replaced with ndbd simply by
       stopping the node and then starting ndbd in place of the multi-threaded 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 (in MySQL Cluster NDB 7.2.3 and later) 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 MySQL Cluster Development and Support
       teams. One trace file is generated for each ndbmtd thread. The names of these files have
       the following pattern:

	   ndb_node_id_trace.log.trace_id_tthread_id,

       In this pattern, node_id stands for the data node's unique node ID in the cluster,
       trace_id is a trace sequence number, and thread_id is the thread ID. For example, in the
       event of the failure of an ndbmtd process running as a MySQL Cluster data node having the
       node ID 3 and with MaxNoOfExecutionThreads equal to 4, four trace files are generated in
       the data node's data directory. If the is the first time this node has failed, then these
       files are named ndb_3_trace.log.1_t1, ndb_3_trace.log.1_t2, ndb_3_trace.log.1_t3, and
       ndb_3_trace.log.1_t4. Internally, these trace files follow the same format as ndbd trace
       files.

       The ndbd exit codes and messages that are generated when a data node process shuts down
       prematurely are also used by ndbmtd. See ndbd Error Messages[1], for a listing of these.

	   Note
	   It is possible to use ndbd and ndbmtd concurrently on different data nodes in the same
	   MySQL Cluster. However, such configurations have not been tested extensively; thus, we
	   cannot recommend doing so in a production setting at this time.

COPYRIGHT
       Copyright (C) 1997, 2014, Oracle and/or its affiliates. All rights reserved.

       This documentation is free software; you can redistribute it and/or modify it only under
       the terms of the GNU General Public License as published by the Free Software Foundation;
       version 2 of the License.

       This documentation is distributed in the hope that it will be useful, but WITHOUT ANY
       WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
       PURPOSE. See the GNU General Public License for more details.

       You should have received a copy of the GNU General Public License along with the program;
       if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
       Boston, MA 02110-1301 USA or see http://www.gnu.org/licenses/.

NOTES
	1. ndbd Error Messages
	   http://dev.mysql.com/doc/ndbapi/en/ndbd-error-messages.html

SEE ALSO
       For more information, please refer to the MySQL Reference Manual, which may already be
       installed locally and which is also available online at http://dev.mysql.com/doc/.

AUTHOR
       Oracle Corporation (http://dev.mysql.com/).

MySQL 5.5				    01/30/2014					NDBMTD(8)
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