Replication and Binary Logging Options and Variables • rpl_read_size • rpl_semi_sync_slave_enabled • rpl_semi_sync_slave_trace_level The  rpl_read_size  system variable controls the minimum amount of data in bytes that is read from the binary log files and relay log files. If heavy disk I/O activity for these files is impeding performance for the database, increasing the read size might reduce file reads and I/O stalls when the file data is not currently cached by the operating system. The minimum and default value for  rpl_read_size  is 8192 bytes. The value must be a multiple of 4KB. Note that a buffer the size of this value is allocated for each thread that reads from the binary log and relay log files, including dump threads on sources and coordinator threads on replicas. Setting a large value might therefore have an impact on memory consumption for servers. Controls whether semisynchronous replication is enabled on the replica server. To enable or disable the plugin, set this variable to  ON  or  OFF  (or 1 or 0), respectively. The default is  OFF . This variable is available only if the replica-side semisynchronous replication plugin is installed. 3526 Command-Line Format --rpl-read-size=# System Variable rpl_read_size Scope Global Dynamic Yes SET_VAR  Hint Applies No Type Integer Default Value 8192 Minimum Value 8192 Maximum Value 4294959104 Block Size 8192 Command-Line Format --rpl-semi-sync-slave-enabled[={OFF| ON}] System Variable rpl_semi_sync_slave_enabled Scope Global Dynamic Yes SET_VAR  Hint Applies No Type Boolean Default Value OFF Command-Line Format --rpl-semi-sync-slave-trace-level=# System Variable rpl_semi_sync_slave_trace_level Scope Global Dynamic Yes SET_VAR  Hint Applies No Type Integer