4.1. MySQL Cluster Manager Usage and Design Limitations

The limitations discussed in this section occur by intention or design in MySQL Cluster Manager 1.1.6. Some of these items may become obsolete in future versions; we will update this section accordingly if and as those changes come about.

change process command.  Currently, the change process command can be used only to exchange an ndbd process for an ndbmtd process, or the reverse. That is, in effect, it can be used only to switch a data node between a single-threaded process and a multi-threaded process. It cannot be used for changing a cluster node's type (for example, you cannot change a data node to an SQL node, management node, or NDB API application node).

Because of this restriction, and due to the fact that multi-threaded data nodes are not supported in MySQL Cluster NDB 6.3 and earlier, the change process command is useful only with clusters running MySQL Cluster NDB 7.0 or newer.

License keys and operating platforms.  License keys were required to use MySQL Cluster Manager 1.0; however, no license key is necessary for MySQL Cluster Manager 1.1.0 or later, including MySQL Cluster Manager 1.1.6.

Concurrent client sessions unsupported.  Currently there is no negotation or arbitration between multiple mcm clients. While it is possible to use the client from multiple locations, we do not support concurrent client sessions. You should be careful always to allow a command issued in one mcm client session to finish executing before issuing a new command in a different client session. This is true especially when using the -B or --background option with mcm client commands; see Backgrounded commands and error handling.

IPv6 and host names (Windows).  When IPv6 support is enabled on Windows systems, host names other than localhost are resolved using IPv6. When an IPv6-enabled Windows system is used as a MySQL Cluster host under MySQL Cluster Manager, you must reference it using its IPv4 address, or as localhost, if this is applicable. Otherwise, mcm will be unable to connect to the agent process on that host.

This applies to host names used with the MySQL Cluster Manager client commands create cluster, create site, add hosts, add package, delete package, stop agents, and add process.