Semisynchronous Replication The number of commits that were not acknowledged successfully by a replica. The number of commits that were acknowledged successfully by a replica. Whether semisynchronous replication currently is operational on the replica. This is 1 if the plugin has been enabled and the replication I/O thread is running, 0 otherwise. The system and status variables are available only if the appropriate source or replica plugin has been installed with  INSTALL PLUGIN . All  Rpl_semi_sync_ xxx  status variables are described at Section 5.1.10, “Server Status Variables” . Semisynchronous replication is implemented using plugins, so the plugins must be installed into the server to make them available. After a plugin has been installed, you control it by means of the system variables associated with it. These system variables are unavailable until the associated plugin has been installed. This section describes how to install the semisynchronous replication plugins. For general information about installing plugins, see Section 5.6.1, “Installing and Uninstalling Plugins” . To use semisynchronous replication, the following requirements must be satisfied: To set up semisynchronous replication, use the following instructions. The  INSTALL PLUGIN ,  SET GLOBAL ,  STOP REPLICA | SLAVE , and  START REPLICA | SLAVE  statements mentioned here require the  REPLICATION_SLAVE_ADMIN  privilege (or the deprecated  SUPER  privilege). MySQL distributions include semisynchronous replication plugin files for the source side and the replica side. To be usable by a source or replica server, the appropriate plugin library file must be located in the MySQL plugin directory (the directory named by the  plugin_dir  system variable). If necessary, configure the plugin directory location by setting the value of  plugin_dir  at server startup. The plugin library file base names are  semisync_master  for the source, and  semisync_slave  for the replica. The file name suffix differs per platform (for example,  .so  for Unix and Unix-like systems,  .dll  for Windows). The source plugin library file must be present in the plugin directory of the source server. The replica plugin library file must be present in the plugin directory of each replica server. To load the plugins, use the  INSTALL PLUGIN  statement on the source and on each replica that is to be semisynchronous, adjusting the  .so  suffix for your platform as necessary. • Rpl_semi_sync_master_yes_tx • Rpl_semi_sync_slave_status •The capability of installing plugins requires a MySQL server that supports dynamic loading. To verify this, check that the value of the  have_dynamic_loading  system variable is  YES . Binary distributions should support dynamic loading. •Replication must already be working, see Section 17.1, “Configuring Replication” . •There must not be multiple replication channels configured. Semisynchronous replication is only compatible with the default replication channel. See Section 17.2.2, “Replication Channels” . 17.4.10.2 Semisynchronous Replication Installation and Configuration 3649