NDB Cluster Replication: Abbreviations and Symbols log injector thread, which runs on each MySQL server and produces a binary log ( binlog ). This thread ensures that all changes in the cluster producing the binary log—and not just those changes that are effected through the MySQL Server—are inserted into the binary log with the correct serialization order. We refer to the MySQL source and replica servers as replication servers or replication nodes, and the data flow or line of communication between them as a  replication channel . For information about performing point-in-time recovery with NDB Cluster and NDB Cluster Replication, see Section 23.6.9.2, “Point-In-Time Recovery Using NDB Cluster Replication” . NDB API replica status variables.   NDB API counters can provide enhanced monitoring capabilities on replica clusters. These counters are implemented as NDB statistics  _slave  status variables, as seen in the output of  SHOW STATUS , or in the results of queries against the Performance Schema session_status  or  global_status  table in a  mysql  client session connected to a MySQL Server that is acting as a replica in NDB Cluster Replication. By comparing the values of these status variables before and after the execution of statements affecting replicated  NDB  tables, you can observe the corresponding actions taken on the NDB API level by the replica, which can be useful when monitoring or troubleshooting NDB Cluster Replication. Section 23.5.13, “NDB API Statistics Counters and Variables” , provides additional information. Replication from NDB to non-NDB tables.   It is possible to replicate  NDB  tables from an NDB Cluster acting as the replication source to tables using other MySQL storage engines such as  InnoDB  or  MyISAM on a replica  mysqld . This is subject to a number of conditions; see Replication from NDB to other storage engines, and Replication from NDB to a nontransactional storage engine, for more information. Throughout this section, we use the following abbreviations or symbols for referring to the source and replica clusters, and to processes and commands run on the clusters or cluster nodes: Table 23.68 Abbreviations used throughout this section referring to source and replica clusters, and to processes and commands run on cluster nodes 23.6.1 NDB Cluster Replication: Abbreviations and Symbols 4610 Symbol or Abbreviation Description (Refers to...) S The cluster serving as the (primary) replication source R The cluster acting as the (primary) replica shell S > Shell command to be issued on the source cluster mysql S > MySQL client command issued on a single MySQL server running as an SQL node on the source cluster mysql S* > MySQL client command to be issued on all SQL nodes participating in the replication source cluster shell R > Shell command to be issued on the replica cluster mysql R > MySQL client command issued on a single MySQL server running as an SQL node on the replica cluster mysql R* > MySQL client command to be issued on all SQL nodes participating in the replica cluster C Primary replication channel C’ Secondary replication channel S’ Secondary replication source