The limitations described in this section relate to functionality in the MySQL Server that is unsupported or reduced, or otherwise differs when using it with MySQL Cluster Manager.

Replication.  Replication is currently not directly supported by MySQL Cluster Manager. See Section 4.3, “MySQL Cluster Manager Limitations Relating to MySQL Cluster”, for more information.

Limited mysqld option modifier support.  MySQL Cluster Manager does not recognize the --loose, --maximum, --enable, and --disable prefixes for mysqld options used as MySQL Cluster Manager configuration attributes (for a description of these modifiers, see Program Option Modifiers). For example, the command set loose-skip-innodb:mysqld=true mycluster; fails with the error No such config variable loose-skip-innodb for process mysqld.

The --skip option modifier is supported in some but not all cases, so that commands such as set skip-innodb:mysqld=true mycluster; and set skip-grant-tables:mysqld=true mycluster; can be used with MySQL Cluster Manager, while set skip-column-names:mysqld=true mycluster; cannot. (Bug #48559, Bug #47779)

Visibility of MySQL Cluster Manager mysqld attributes and MySQL server variables.  Due in part to issues with mappings between my.cnf option names, mysqld command-line option names, and names of MySQL server variables, some MySQL server variables are not visible to MySQL Cluster Manager, or have different names. For example, the storage_engine server variable shown in the output of SHOW VARIABLES in the mysql client maps to the default-storage-engine configuration attribute used in the MySQL Cluster Manager get and set commands.

Dashes and underscores in MySQL option and variable names.  When using the mysql client or other MySQL client applications, many MySQL system options and variables can be named using either dashes or underscores in their names. For example, you can use either ndb_batch_size or ndb-batch-size with the MySQL Server, and the variable is set correctly. This is not the case in MySQL Cluster Manager, where only the forms using underscores are accepted as attribute names. For example, assuming that mycluster is a viable cluster, the command set ndb_batch_size:mysqld=65536 mycluster; works to set the size of ndb_batch_size on all mysqld processes in the cluster, but set ndb-batch-size:mysqld=65536 mycluster; fails.

Dependencies between MySQL Cluster Manager mysqld attributes and MySQL server variables.  MySQL Cluster Manager does not track dependencies between mysqld attributes (MySQL server options and variables). For example, MySQL Server 5.1 and earlier require, when the binlog_format attribute is set, that the log_bin attribute be used as well; if binlog_format is used without log_bin, mysqld fails to start (MySQL Server Bug #42928, fixed in MySQL 5.5 and MySQL Cluster NDB 7.2). If you do this using MySQL Cluster Manager, however, the MySQL Cluster Manager agent reports that the operation was started successfully, and from MySQL Cluster Manager's point of view, this is correct—MySQL Cluster Manager started the mysqld process with the indicated attribute settings, and it is up to the operator to verify that the result was the one expected. In such cases, it is a good idea to check the status of the mysqld process, perhaps using show status --operation, before continuing.

MySQL Cluster Manager mysqld attributes and MySQL user variables.  MySQL user variables are not accessible as MySQL Cluster Manager configuration attributes.