21.3.2 Overview of NDB Cluster Configuration Parameters, Options, and Variables
The next several sections provide summary tables of NDB Cluster node configuration parameters used in the
config.ini file to govern various aspects of node behavior, as well as of options and variables read by mysqld from a
my.cnf file or from the command line when run as an NDB Cluster process. Each of the node parameter tables lists the parameters for a given type (
shm). All tables include the data type for the parameter, option, or variable, as well as its default, mimimum, and maximum values as applicable.
Considerations when restarting nodes. For node parameters, these tables also indicate what type of restart is required (node restart or system restart)—and whether the restart must be done with
--initial—to change the value of a given configuration parameter. When performing a node restart or an initial node restart, all of the cluster's data nodes must be restarted in turn (also referred to as a rolling restart). It is possible to update cluster configuration parameters marked as
node online—that is, without shutting down the cluster—in this fashion. An initial node restart requires restarting each ndbd process with the
A system restart requires a complete shutdown and restart of the entire cluster. An initial system restart requires taking a backup of the cluster, wiping the cluster file system after shutdown, and then restoring from the backup following the restart.
In any cluster restart, all of the cluster's management servers must be restarted for them to read the updated configuration parameter values.
Values for numeric cluster parameters can generally be increased without any problems, although it is advisable to do so progressively, making such adjustments in relatively small increments. Many of these can be increased online, using a rolling restart.
However, decreasing the values of such parameters—whether this is done using a node restart, node initial restart, or even a complete system restart of the cluster—is not to be undertaken lightly; it is recommended that you do so only after careful planning and testing. This is especially true with regard to those parameters that relate to memory usage and disk space, such as
MaxNoOfUniqueHashIndexes. In addition, it is the generally the case that configuration parameters relating to memory and disk usage can be raised using a simple node restart, but they require an initial node restart to be lowered.
Because some of these parameters can be used for configuring more than one type of cluster node, they may appear in more than one of the tables.
4294967039 often appears as a maximum value in these tables. This value is defined in the
NDBCLUSTER sources as
MAX_INT_RNIL and is equal to
232 - 28 - 1.