Replication SQL Thread States The thread is trying to reconnect to the source. When connection is established again, the state becomes  Waiting for master to send event . A state that occurs very briefly after the connection to the source is established. A state that occurs very briefly, after the connection to the source is established. The thread sends to the source a request for the contents of its binary logs, starting from the requested binary log file name and position. A state that occurs when the replica thread is waiting for older worker threads to commit if slave_preserve_commit_order  is enabled. The thread has connected to the source and is waiting for binary log events to arrive. This can last for a long time if the source is idle. If the wait lasts for  slave_net_timeout  seconds, a timeout occurs. At that point, the thread considers the connection to be broken and makes an attempt to reconnect. A state that occurs briefly as the thread is stopping. You are using a nonzero  relay_log_space_limit  value, and the relay logs have grown large enough that their combined size exceeds this value. The I/O thread is waiting until the SQL thread frees enough space by processing relay log contents so that it can delete some relay log files. If the binary log dump request failed (due to disconnection), the thread goes into this state while it sleeps, then tries to reconnect periodically. The interval between retries can be specified using the the  CHANGE REPLICATION SOURCE TO  statement (from MySQL 8.0.23) or  CHANGE MASTER TO statement (before MySQL 8.0.23). An error occurred while reading (due to disconnection). The thread is sleeping for the number of seconds set by the the  CHANGE REPLICATION SOURCE TO  statement (from MySQL 8.0.23) or  CHANGE MASTER TO  statement (before MySQL 8.0.23), which defaults to 60, before attempting to reconnect. The following list shows the most common states you may see in the  State  column for a replication SQL thread on a replica server: •  Making temporary file (append) before replaying LOAD DATA INFILE 8.14.6 Replication SQL Thread States 1855 •  Waiting to reconnect after a failed master event read •  Waiting to reconnect after a failed binlog dump request •  Waiting for the slave SQL thread to free enough relay log space •  Waiting for slave mutex on exit •  Waiting for master update The initial state before  Connecting to master . •  Waiting for master to send event •  Waiting for its turn to commit •  Requesting binlog dump •  Registering slave on master