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## 17.2.2.2 Compatibility with Previous Replication Statements 

When a replica has multiple channels and a FOR CHANNEL channel  option is not specified, a valid statement generally acts on all available channels, with some specific exceptions. 

For example, the following statements behave as expected for all except certain Group Replication channels: 

• START REPLICA | SLAVE  starts replication threads for all channels, except the group_replication_recovery  and group_replication_applier  channels. 

• STOP REPLICA | SLAVE  stops replication threads for all channels, except the group_replication_recovery  and group_replication_applier  channels. 

• SHOW REPLICA | SLAVE STATUS  reports the status for all channels, except the group_replication_applier  channel. 

• RESET REPLICA | SLAVE  resets all channels. 

<img src='content_image/763885.jpg'>

## Warning 

Use RESET REPLICA | SLAVE  with caution as this statement deletes all existing channels, purges their relay log files, and recreates only the default channel. 

Some replication statements cannot operate on all channels. In this case, error 1964 Multiple channels exist on the replica. Please provide channel name as an argument. is generated. The following statements and functions generate this error when used in a multi-source replication topology and a FOR CHANNEL channel  option is not used to specify which channel to act on: 

• SHOW RELAYLOG EVENTS 

• CHANGE REPLICATION SOURCE TO 

• CHANGE MASTER TO 

• MASTER_POS_WAIT() 

Note that a default channel always exists in a single source replication topology, where statements and functions behave as in previous versions of MySQL. 

## 17.2.2.3 Startup Options and Replication Channels 

This section describes startup options which are impacted by the addition of replication channels. 

The master_info_repository  and relay_log_info_repository  system variables must not  be set to FILE  when you use replication channels. In MySQL 8.0, the FILE  setting is deprecated, and TABLE  is the default, so the system variables can be omitted. From MySQL 8.0.23, they must be omitted because their use is deprecated from that release. If these system variables are set to FILE , attempting to add more sources to a replica fails with ER_SLAVE_NEW_CHANNEL_WRONG_REPOSITORY . 

The following startup options now affect all  channels in a replication topology. 

• --log-slave-updates 

All transactions received by the replica (even from multiple sources) are written in the binary log. 

• --relay-log-purge 

