MySQL 5.7 Reference Manual Including MySQL NDB Cluster 7.5 and NDB Cluster 7.6

8.14.5 Replication Slave I/O Thread States

The following list shows the most common states you see in the State column for a slave server I/O thread. This state also appears in the Slave_IO_State column displayed by SHOW SLAVE STATUS, so you can get a good view of what is happening by using that statement.