The server detects multiple replication channels on the slave but the issued command does not specify which channel to target.
ER_SLAVE_MULTIPLE_CHANNELS_CMD (error 3079) arises when you run a replication command on a MySQL slave that has more than one channel but omit the CHANNEL clause. Specify the channel name or use a wildcard to resolve the error.
ER_SLAVE_MULTIPLE_CHANNELS_CMD
Error 3079 appears when a replication statement such as START SLAVE, STOP SLAVE, SHOW RELAYLOG EVENTS, or CHANGE MASTER is executed on a MySQL replica configured with multiple replication channels without specifying which channel the command should operate on.
MySQL 5.7.6 and later support multi-source replication, allowing several masters to send data to one replica over separate channels. Because each channel maintains its own relay logs and execution state, ambiguous commands are blocked by the server to prevent accidental changes.
The error is triggered by any replication management command that must target a single channel while the replica hosts two or more channels.
It also occurs if a DBA removes a channel but the metadata still lists multiple channels, leaving the server unsure which channel to act on.
Always include the FOR CHANNEL 'channel_name' clause in replication commands. If you truly intend to run the command on all channels, loop through the list returned by SHOW SLAVE STATUS and execute the statement for each channel.
Consider setting up a Galaxy workspace with your MySQL connection so that endorsed SQL snippets for replication maintenance already include the correct CHANNEL clause, preventing typos and saving time.
Stopping replication during maintenance: use STOP SLAVE FOR CHANNEL 'sales_feed'.
Changing master credentials for one source: use CHANGE MASTER TO MASTER_USER='repl',MASTER_PASSWORD='********' FOR CHANNEL 'inventory_feed'.
Resetting all replication metadata: iterate over channels and run RESET SLAVE FOR CHANNEL 'channel_name'.
Document channel names and keep them consistent across environments.
Store replication scripts in Galaxy Collections so your team reuses vetted commands.
Monitor SHOW SLAVE STATUS regularly and alert when channels are added or dropped unexpectedly.
ER_SLAVE_CHANNEL_DOES_NOT_EXIST (3085) - occurs when you reference a channel that is not defined. Create the channel first or correct the name.
ER_SLAVE_MULTIPLE_CHANNELS_CMD (3079) differs from ER_SLAVE_CHANNEL_DOES_NOT_EXIST in that the first signals ambiguity while the second signals an invalid channel name.
The DBA runs START SLAVE or STOP SLAVE without specifying FOR CHANNEL.
Legacy maintenance scripts are unaware that multiple replication channels now exist.
Channels were dropped manually but metadata still reflects more than one channel due to incomplete cleanup.
Third-party management tools issue generic replication commands that lack channel context.
Triggered when a command references an undefined channel. Verify channel names.
Raised when attempting to drop the last remaining channel. Remove replication entirely or keep at least one channel.
Occurs when MySQL cannot allocate a new channel due to memory or name conflicts.
No single command stops all channels. Loop through each channel returned by SHOW SLAVE STATUS or use a management script.
ER_SLAVE_MULTIPLE_CHANNELS_CMD was introduced in MySQL 5.7.6 and remains through the latest 8.x releases.
The command fails with error 3079, protecting each channel from unintended modifications.
Galaxy Collections let teams store tested replication commands that already include the correct FOR CHANNEL clause, reducing human error.
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