MySQL 5.6 Reference Manual Including MySQL NDB Cluster 7.3-7.4 Reference Guide NDB Cluster Shared-Memory Connections

NDB Cluster attempts to use the shared memory transporter and configure it automatically where possible. [shm] sections in the config.ini file explicitly define shared-memory connections between nodes in the cluster. When explicitly defining shared memory as the connection method, it is necessary to define at least NodeId1, NodeId2, and ShmKey. All other parameters have default values that should work well in most cases.


SHM functionality is considered experimental only. It is not officially supported in any current NDB Cluster release, and testing results indicate that SHM performance is not appreciably greater than when using TCP/IP for the transporter.

For these reasons, you must determine for yourself or by using our free resources (forums, mailing lists) whether SHM can be made to work correctly in your specific case.

Restart types.  Information about the restart types used by the parameter descriptions in this section is shown in the following table:

Table 18.16 NDB Cluster restart types

Symbol Restart Type Description
N Node The parameter can be updated using a rolling restart (see Section 18.5.5, “Performing a Rolling Restart of an NDB Cluster”)
S System All cluster nodes must be shut down completely, then restarted, to effect a change in this parameter
I Initial Data nodes must be restarted using the --initial option