<p>The error appears when you attempt to start only the replica SQL thread while also passing authentication parameters, which MySQL disallows.</p>
<p>MySQL Error 1763 ER_SQLTHREAD_WITH_SECURE_SLAVE occurs when the START SLAVE SQL_THREAD command includes authentication options. Start the full replica or omit the options to clear the error.</p>
Setting authentication options is not possible when only
The message “Setting authentication options is not possible when only the Slave SQL Thread is being started” signals that MySQL replication refuses to apply new authentication settings while you launch only the SQL thread.
MySQL expects the I/O thread to establish credentials first. Mixing partial starts with security options breaks this requirement and raises error 1763.
The START SLAVE SQL_THREAD or START REPLICA SQL_THREAD statement is issued together with MASTER_USER, MASTER_PASSWORD, or CHANNEL-related TLS settings. Because the I/O thread stays stopped, MySQL blocks the operation for security consistency.
This check prevents a replica from applying relay logs with mismatched or unverified credentials, protecting data integrity.
Launch the replica with a full START SLAVE/REPLICA to initialize both I/O and SQL threads using the new credentials. Alternatively, omit authentication clauses when starting only the SQL thread.
If you must adjust credentials, execute CHANGE MASTER TO (or CHANGE REPLICATION SOURCE TO) with the desired options, then run START SLAVE; without the SQL_THREAD qualifier.
During failover, ops teams often start SQL_THREAD to catch up after importing relay logs. Ensure authentication is unchanged or start both threads.
Automated scripts that rotate passwords may embed MASTER_PASSWORD in every START command. Refactor the script to separate credential rotation from thread restarts.
Always use CHANGE MASTER TO for credential updates, then run a full START SLAVE. Document and version control replication commands to avoid accidental parameter mixing.
Monitor replica status with SHOW SLAVE STATUS or performance_schema replication tables. Alert on Last_SQL_Errno = 1763 so you can remediate quickly.
Error 1751 (ER_SLAVE_RELAY_LOG_WRITE_FAILURE) indicates relay log write problems. Confirm disk space and permissions.
Error 1872 (ER_SLAVE_WAS_NOT_RUNNING) appears when STOP SLAVE is issued on an already stopped replica. Check thread status before stopping.
Supplying MASTER_USER or MASTER_PASSWORD while limiting the start to SQL_THREAD triggers the security check.
START REPLICA SQL_THREAD with REQUIRE_SSL or certificates configured fails because secure channel validation occurs in the I/O thread.
Custom scripts that always append authentication parameters to START commands cause the error during partial restarts.
Occurs when the replica cannot write relay logs due to disk or permission issues.
Raised when STOP SLAVE is executed on a replica that is already stopped.
Happens if you set a replication delay outside the allowed range.
No. The replica will not start the SQL thread with new credentials, so data will stop replicating until fixed.
No. It exists in MySQL 5.7 and 8.0 series. Behavior is consistent across versions.
Starting both threads is normal operation. It will not hurt performance and is required for credential changes.
Galaxy's query templates and versioned snippets let teams store correct replication commands, reducing chances of mixing options.
.avif)
.avif){kind=logo}
