<p>MySQL Error 1794 appears when a replica (slave) server is started without the mandatory server-id or other replication parameters, preventing the replication thread from initializing.</p>
<p>MySQL Error 1794: ER_SLAVE_CONFIGURATION means the replica server lacks a proper server-id or has an invalid replication setup. Set a unique server-id and verify replication parameters, then restart MySQL to resolve the issue.</p>
Slave is not configured or failed to initialize properly.
MySQL raises Error 1794 with message "Slave is not configured or failed to initialize properly" when the replication thread starts but finds no valid configuration. The error stops the replica from connecting to the primary server.
The condition name ER_SLAVE_CONFIGURATION commonly appears during initial replica setup or after a configuration change that removes critical replication variables.
Fixing it quickly is vital because a stalled replica can break high availability, delay backups, and cause data divergence across environments.
Error 1794 fires when the server-id variable is missing or duplicated, making the instance indistinguishable in the replication topology.
It also occurs if log_bin is disabled on the primary, relay-log parameters are wrong, or essential tables in the mysql system schema are corrupted.
Assign a unique server-id in my.cnf, verify log_bin and binlog_format, and ensure replica metadata tables exist. Restart MySQL to apply the changes.
If you changed replication accounts, update CHANGE REPLICATION SOURCE TO with the correct user, password, host, and port.
After cloning a production server, the clone shares the same server-id and triggers Error 1794 on boot. Edit my.cnf to set a new server-id and restart.
Upgrading MySQL may reset relay-log paths. Confirm relay-log and relay-log-index paths are valid and writable, then run RESET SLAVE to recreate relay files.
Use configuration management to enforce unique server-id values across all replicas. Automate checks during provisioning.
Monitor MySQL error logs and replication status (SHOW REPLICA STATUS) to catch misconfigurations before they cascade.
Error 1201 (ER_SLAVE_THREAD): Starts when IO/SQL threads stop due to config issues. Verify network and replication user permissions.
Error 1872 (ER_SLAVE_DELAYED_INIT): Indicates delayed replica start. Check replication lag and configuration settings.
MySQL replication requires a unique nonzero server-id. Without it, the replica cannot register with the primary.
If log_bin is off on the primary, the replica cannot retrieve binary logs, triggering initialization failure.
Invalid or unwritable relay log directories prevent the replication SQL thread from starting.
Metadata corruption stops replication threads during startup validation.
Replica IO/SQL threads stopped. Often follows Error 1794 if config errors persist.
Replica start delayed by configuration or system load. Check thread status.
Fatal error on replica SQL thread due to data mismatch or corrupt relay logs.
You cannot. server-id is a static variable and requires a restart after changing my.cnf.
No. Each instance in a replication topology, primary or replica, must have a unique server-id.
Yes. Group Replication also relies on server-id. Misconfiguration prevents the node from joining the group.
Galaxy's SQL editor surfaces server variables and error logs in one view, allowing engineers to spot missing server-id values before deployment.
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