MySQL 8.4 Release Notes
Once you have added channels for all of the replication sources,
issue a START REPLICA statement to
start replication. When you have enabled multiple channels on a
replica, you can choose to either start all channels, or select a
specific channel to start. For example, to start the two channels
separately, use the mysql client to issue the
following statements:
mysql> START REPLICA FOR CHANNEL "source_1";
mysql> START REPLICA FOR CHANNEL "source_2";
For the full syntax of the START
REPLICA statement and other available options, see
Section 15.4.2.4, “START REPLICA Statement”.
To verify that both channels have started and are operating
correctly, you can issue SHOW REPLICA
STATUS statements on the replica, for example:
mysql> SHOW REPLICA STATUS FOR CHANNEL "source_1"\G
mysql> SHOW REPLICA STATUS FOR CHANNEL "source_2"\G