Replication and Binary Logging Options and Variables • rpl_semi_sync_master_wait_for_slave_count The number of replica acknowledgments the source must receive per transaction before proceeding. By default  rpl_semi_sync_master_wait_for_slave_count  is  1 , meaning that semisynchronous replication proceeds after receiving a single replica acknowledgment. Performance is best for small values of this variable. For example, if  rpl_semi_sync_master_wait_for_slave_count  is  2 , then 2 replicas must acknowledge receipt of the transaction before the timeout period configured by rpl_semi_sync_master_timeout  for semisynchronous replication to proceed. If fewer replicas acknowledge receipt of the transaction during the timeout period, the source reverts to normal replication. This behavior also depends on  rpl_semi_sync_master_wait_no_slave This variable is available only if the source-side semisynchronous replication plugin is installed. Controls whether the source waits for the timeout period configured by rpl_semi_sync_master_timeout  to expire, even if the replica count drops to less than the number of replicas configured by  rpl_semi_sync_master_wait_for_slave_count  during the timeout period. When the value of  rpl_semi_sync_master_wait_no_slave  is  ON  (the default), it is permissible for the replica count to drop to less than  rpl_semi_sync_master_wait_for_slave_count  during 3503 • rpl_semi_sync_master_wait_no_slave Note Command-Line Format --rpl-semi-sync-master-wait-no- slave[={OFF|ON}] System Variable rpl_semi_sync_master_wait_no_slave Scope Global Dynamic Yes SET_VAR  Hint Applies No Type Boolean Default Value ON Command-Line Format --rpl-semi-sync-master-wait-for- slave-count=# System Variable rpl_semi_sync_master_wait_for_slave_count Scope Global Dynamic Yes SET_VAR  Hint Applies No Type Integer Default Value 1 Minimum Value 1 Maximum Value 65535