Replication and Binary Logging Options and Variables If something goes wrong such that the replica does not process the transaction, then in the event of an unexpected source server exit and failover to the replica, it is possible for such clients to see a loss of data relative to what they saw on the source. This variable is available only if the source-side semisynchronous replication plugin is installed. With the addition of  rpl_semi_sync_master_wait_point  in MySQL 5.7, a version compatibility constraint was created because it increments the semisynchronous interface version: Servers for MySQL 5.7 and higher do not work with semisynchronous replication plugins from older versions, nor do servers from older versions work with semisynchronous replication plugins for MySQL 5.7 and higher. This section explains the server options and system variables that apply to replica servers and contains the following: Specify the options either on the command line or in an option file. Many of the options can be set while the server is running by using the  CHANGE REPLICATION SOURCE TO  statement (from MySQL 8.0.23) or CHANGE MASTER TO  statement (before MySQL 8.0.23). Specify system variable values using  SET . Server ID.   On the source and each replica, you must set the  server_id  system variable to establish a unique replication ID in the range from 1 to 2$^{32}$  − 1. “Unique”  means that each ID must be different from every other ID in use by any other source or replica in the replication topology. Example  my.cnf  file: This section explains startup options for controlling replica servers. Many of these options can be set while the server is running by using the  CHANGE REPLICATION SOURCE TO  statement (from MySQL 8.0.23) or  CHANGE MASTER TO  statement (before MySQL 8.0.23). Others, such as the  --replicate-*  options, can be set only when the replica server starts. Replication-related system variables are discussed later in this section. The use of this option is now deprecated. It was used to set the file name for the replica’s connection metadata repository if  master_info_repository=FILE  was set.  --master-info-file  and the use of the  master_info_repository  system variable are deprecated because the use of a file for the connection metadata repository has been superseded by crash-safe tables. For information about the connection metadata repository, see Section 17.2.4.2, “Replication Metadata Repositories” . 3505 • --master-retry-count= count • --master-info-file= file_name Startup Options for Replica Servers 17.1.6.3 Replica Server Options and Variables •Startup Options for Replica Servers •System Variables Used on Replica Servers [mysqld] server-id=3 Command-Line Format --master-info-file=file_name Deprecated 8.0.18 Type File name Default Value master.info Command-Line Format --master-retry-count=#