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Excerpts from this Manual CHANGE MASTER TO Syntax

CHANGE MASTER TO option [, option] ... [ channel_option ]

    MASTER_BIND = 'interface_name'
  | MASTER_HOST = 'host_name'
  | MASTER_USER = 'user_name'
  | MASTER_PASSWORD = 'password'
  | MASTER_PORT = port_num
  | MASTER_DELAY = interval
  | MASTER_LOG_FILE = 'master_log_name'
  | MASTER_LOG_POS = master_log_pos
  | RELAY_LOG_FILE = 'relay_log_name'
  | RELAY_LOG_POS = relay_log_pos
  | MASTER_SSL = {0|1}
  | MASTER_SSL_CA = 'ca_file_name'
  | MASTER_SSL_CAPATH = 'ca_directory_name'
  | MASTER_SSL_CERT = 'cert_file_name'
  | MASTER_SSL_CRL = 'crl_file_name'
  | MASTER_SSL_CRLPATH = 'crl_directory_name'
  | MASTER_SSL_KEY = 'key_file_name'
  | MASTER_SSL_CIPHER = 'cipher_list'
  | MASTER_TLS_VERSION = 'protocol_list'
  | IGNORE_SERVER_IDS = (server_id_list)

    FOR CHANNEL channel

    [server_id [, server_id] ... ]

CHANGE MASTER TO changes the parameters that the slave server uses for connecting to the master server, for reading the master binary log, and reading the slave relay log. It also updates the contents of the master info and relay log info repositories (see Section 16.2.4, “Replication Relay and Status Logs”). CHANGE MASTER TO requires the SUPER privilege.

Prior to MySQL 5.7.4, the slave replication threads must be stopped, using STOP SLAVE if necessary, before issuing this statement. In MySQL 5.7.4 and later, you can issue CHANGE MASTER TO statements on a running slave without doing this, depending on the states of the slave SQL thread and slave I/O thread. The rules governing such use are provided later in this section.

When using a multi-threaded slave (in other words slave_parallel_workers is greater than 0), stopping the slave can cause gaps in the sequence of transactions that have been executed from the relay log, regardless of whether the slave was stopped intentionally or otherwise. When such gaps exist, issuing CHANGE MASTER TO fails. The solution in this situation is to issue START SLAVE UNTIL SQL_AFTER_MTS_GAPS which ensures that the gaps are closed.

The optional FOR CHANNEL channel clause enables you to name which replication channel the statement applies to. Providing a FOR CHANNEL channel clause applies the CHANGE MASTER TO statement to a specific replication channel, and is used to add a new channel or modify an existing channel. For example, to add a new channel called channel2:


If no clause is named and no extra channels exist, the statement applies to the default channel.

When using multiple replication channels, if a CHANGE MASTER TO statement does not name a channel using a FOR CHANNEL channel clause, an error occurs. See Section 16.2.3, “Replication Channels” for more information.

Options not specified retain their value, except as indicated in the following discussion. Thus, in most cases, there is no need to specify options that do not change. For example, if the password to connect to your MySQL master has changed, issue this statement to tell the slave about the new password:


MASTER_HOST, MASTER_USER, MASTER_PASSWORD, and MASTER_PORT provide information to the slave about how to connect to its master:

  • MASTER_HOST and MASTER_PORT are the host name (or IP address) of the master host and its TCP/IP port.


    Replication cannot use Unix socket files. You must be able to connect to the master MySQL server using TCP/IP.

    If you specify the MASTER_HOST or MASTER_PORT option, the slave assumes that the master server is different from before (even if the option value is the same as its current value.) In this case, the old values for the master binary log file name and position are considered no longer applicable, so if you do not specify MASTER_LOG_FILE and MASTER_LOG_POS in the statement, MASTER_LOG_FILE='' and MASTER_LOG_POS=4 are silently appended to it.

    Setting MASTER_HOST='' (that is, setting its value explicitly to an empty string) is not the same as not setting MASTER_HOST at all. Beginning with MySQL 5.5, trying to set MASTER_HOST to an empty string fails with an error. Previously, setting MASTER_HOST to an empty string caused START SLAVE subsequently to fail. (Bug #28796)

    Values used for MASTER_HOST and other CHANGE MASTER TO options are checked for linefeed (\n or 0x0A) characters; the presence of such characters in these values causes the statement to fail with ER_MASTER_INFO. (Bug #11758581, Bug #50801)

  • MASTER_USER and MASTER_PASSWORD are the user name and password of the account to use for connecting to the master.

    MASTER_USER cannot be made empty; setting MASTER_USER = '' or leaving it unset when setting a value for MASTER_PASSWORD causes an error (Bug #13427949).

    The password used for a MySQL Replication slave account in a CHANGE MASTER TO statement is limited to 32 characters in length; prior to MySQL 5.7.5, if the password was longer, the statement succeeded, but any excess characters were silently truncated. In MySQL 5.7.5 and later, trying to use a password of more than 32 characters causes CHANGE MASTER TO to fail. (Bug #11752299, Bug #43439)

    The text of a running CHANGE MASTER TO statement, including values for MASTER_USER and MASTER_PASSWORD, can be seen in the output of a concurrent SHOW PROCESSLIST statement. (The complete text of a START SLAVE statement is also visible to SHOW PROCESSLIST.)

The MASTER_SSL_xxx options provide information about using SSL for the connection. They correspond to the --ssl-xxx options described in Section 6.4.2, “Command Options for Secure Connections”, and Section 16.3.8, “Setting Up Replication to Use Secure Connections”. These options can be changed even on slaves that are compiled without SSL support. They are saved to the master info repository, but are ignored if the slave does not have SSL support enabled.

As of MySQL 5.7.3, the MASTER_SSL=1 is prescriptive, not advisory. When given, the slave connection to the master must use SSL or the connection attempt fails. Before 5.7.3, an SSL connection is permitted but not required. This is analogous to the client-side meaning of the --ssl command-line option; see Section 6.4.2, “Command Options for Secure Connections”.

The MASTER_TLS_VERSION option specifies the encryption protocols permitted by the master for slave connections. The value is like that for the tls_version system variable: A comma-separated list containing one or more protocol names. The protocols that can be named for this option depend on the SSL library used to compile MySQL. For details, see Section 6.4.6, “Secure Connection Protocols and Ciphers”. This option was added in MySQL 5.7.10.

MASTER_CONNECT_RETRY specifies how many seconds to wait between connect retries. The default is 60.

MASTER_RETRY_COUNT limits the number of reconnection attempts and updates the value of the Master_Retry_Count column in the output of SHOW SLAVE STATUS. The default value is 24 * 3600 = 86400. MASTER_RETRY_COUNT is intended to replace the older --master-retry-count server option, and is now the preferred method for setting this limit. You are encouraged not to rely on --master-retry-count in new applications and, when upgrading to MySQL 5.7, to update any existing applications that rely on it, so that they use CHANGE MASTER TO ... MASTER_RETRY_COUNT instead.

MASTER_DELAY specifies how many seconds behind the master the slave must lag. An event received from the master is not executed until at least interval seconds later than its execution on the master. The default is 0. An error occurs if interval is not a nonnegative integer in the range from 0 to 231−1. For more information, see Section 16.3.10, “Delayed Replication”.

In MySQL 5.7.4 and later, a CHANGE MASTER TO statement employing the MASTER_DELAY option can be executed on a running slave when the slave SQL thread is stopped.

MASTER_BIND is for use on replication slaves having multiple network interfaces, and determines which of the slave's network interfaces is chosen for connecting to the master.

The address configured with this option, if any, can be seen in the Master_Bind column of the output from SHOW SLAVE STATUS. If you are using slave status log tables (server started with --master-info-repository=TABLE), the value can also be seen as the Master_bind column of the mysql.slave_master_info table.

The ability to bind a replication slave to a specific network interface is also supported by NDB Cluster.

MASTER_HEARTBEAT_PERIOD sets the interval in seconds between replication heartbeats. Whenever the master's binary log is updated with an event, the waiting period for the next heartbeat is reset. interval is a decimal value having the range 0 to 4294967 seconds and a resolution in milliseconds; the smallest nonzero value is 0.001. Heartbeats are sent by the master only if there are no unsent events in the binary log file for a period longer than interval.

Prior to MySQL 5.7.4, not including MASTER_HEARTBEAT_PERIOD caused CHANGE MASTER TO to reset the heartbeat period (Slave_heartbeat_period) to the default, and Slave_received_heartbeats to 0. (Bug #18185490)

If you are logging master connection information to tables, MASTER_HEARTBEAT_PERIOD can be seen as the value of the Heartbeat column of the mysql.slave_master_info table.

Setting interval to 0 disables heartbeats altogether. The default value for interval is equal to the value of slave_net_timeout divided by 2.

Setting @@global.slave_net_timeout to a value less than that of the current heartbeat interval results in a warning being issued. The effect of issuing RESET SLAVE on the heartbeat interval is to reset it to the default value.

MASTER_LOG_FILE and MASTER_LOG_POS are the coordinates at which the slave I/O thread should begin reading from the master the next time the thread starts. RELAY_LOG_FILE and RELAY_LOG_POS are the coordinates at which the slave SQL thread should begin reading from the relay log the next time the thread starts. If you specify either of MASTER_LOG_FILE or MASTER_LOG_POS, you cannot specify RELAY_LOG_FILE or RELAY_LOG_POS. If you specify either of MASTER_LOG_FILE or MASTER_LOG_POS, you also cannot specify MASTER_AUTO_POSITION = 1 (described later in this section). If neither of MASTER_LOG_FILE or MASTER_LOG_POS is specified, the slave uses the last coordinates of the slave SQL thread before CHANGE MASTER TO was issued. This ensures that there is no discontinuity in replication, even if the slave SQL thread was late compared to the slave I/O thread, when you merely want to change, say, the password to use.

In MySQL 5.7.4 and later, a CHANGE MASTER TO statement employing RELAY_LOG_FILE, RELAY_LOG_POS, or both options can be executed on a running slave when the slave SQL thread is stopped.

If MASTER_AUTO_POSITION = 1 is used with CHANGE MASTER TO, the slave attempts to connect to the master using the GTID-based replication protocol. In MySQL 5.7.4 and later, this option can be employed by CHANGE MASTER TO only if both the slave SQL and slave I/O threads are stopped.

When using GTIDs, the slave tells the master which transactions it has already received, executed, or both. To compute this set, it reads the global value of gtid_executed and the value of the Retrieved_gtid_set column from SHOW SLAVE STATUS. The GTID of the last transmitted transaction is included in Retrieved_gtid_set only when the full transaction is received. The slave computes the following set:

UNION(@@global.gtid_executed, Retrieved_gtid_set)

Prior to MySQL 5.7.5, the GTID of the last transmitted transaction was included in Retrieved_gtid_set even if the transaction was only partially transmitted, and the last received GTID was subtracted from this set. (Bug #17943188) Thus, the slave computed the following set:

UNION(@@global.gtid_executed, Retrieved_gtid_set - last_received_GTID)

This set is sent to the master as part of the initial handshake, and the master sends back all transactions that it has executed which are not part of the set. If any of these transactions have been already purged from the master's binary log, the master sends the error ER_MASTER_HAS_PURGED_REQUIRED_GTIDS to the slave, and replication does not start.

When GTID-based replication is employed, the coordinates represented by MASTER_LOG_FILE and MASTER_LOG_POS are not used, and global transaction identifiers are used instead. Thus the use of either or both of these options together with MASTER_AUTO_POSITION causes an error.

Beginning with MySQL 5.7.1, you can see whether replication is running with autopositioning enabled by checking the output of SHOW SLAVE STATUS. (Bug #15992220)

gtid_mode must also be enabled before issuing CHANGE MASTER TO ... MASTER_AUTO_POSITION = 1. Otherwise, the statement fails with an error.

To revert to the older file-based replication protocol after using GTIDs, you can issue a new CHANGE MASTER TO statement that specifies MASTER_AUTO_POSITION = 0, as well as at least one of MASTER_LOG_FILE or MASTER_LOG_POS.

Prior to MySQL 5.7.4, CHANGE MASTER TO deletes all relay log files and starts a new one, unless you specify RELAY_LOG_FILE or RELAY_LOG_POS. In that case, relay log files are kept; the relay_log_purge global variable is set silently to 0. In MySQL 5.7.4 and later, relay logs are preserved if at least one of the slave SQL thread and the slave I/O thread is running; if both threads are stopped, all relay log files are deleted unless at least one of RELAY_LOG_FILE or RELAY_LOG_POS is specified.

RELAY_LOG_FILE can use either an absolute or relative path, and uses the same base name as MASTER_LOG_FILE. (Bug #12190)

IGNORE_SERVER_IDS takes a comma-separated list of 0 or more server IDs. Events originating from the corresponding servers are ignored, with the exception of log rotation and deletion events, which are still recorded in the relay log.

In circular replication, the originating server normally acts as the terminator of its own events, so that they are not applied more than once. Thus, this option is useful in circular replication when one of the servers in the circle is removed. Suppose that you have a circular replication setup with 4 servers, having server IDs 1, 2, 3, and 4, and server 3 fails. When bridging the gap by starting replication from server 2 to server 4, you can include IGNORE_SERVER_IDS = (3) in the CHANGE MASTER TO statement that you issue on server 4 to tell it to use server 2 as its master instead of server 3. Doing so causes it to ignore and not to propagate any statements that originated with the server that is no longer in use.

If a CHANGE MASTER TO statement is issued without any IGNORE_SERVER_IDS option, any existing list is preserved. To clear the list of ignored servers, it is necessary to use the option with an empty list:


Prior to MySQL 5.7.5, RESET SLAVE ALL has no effect on the server ID list. In MySQL 5.7.5 and later, RESET SLAVE ALL clears IGNORE_SERVER_IDS. (Bug #18816897)

If IGNORE_SERVER_IDS contains the server's own ID and the server was started with the --replicate-same-server-id option enabled, an error results.

In MySQL 5.7, the master info repository and the output of SHOW SLAVE STATUS provide the list of servers that are currently ignored. For more information, see Section, “Slave Status Logs”, and Section, “SHOW SLAVE STATUS Syntax”.

In MySQL 5.7, invoking CHANGE MASTER TO causes the previous values for MASTER_HOST, MASTER_PORT, MASTER_LOG_FILE, and MASTER_LOG_POS to be written to the error log, along with other information about the slave's state prior to execution.

In MySQL 5.7, CHANGE MASTER TO causes an implicit commit of an ongoing transaction. See Section 13.3.3, “Statements That Cause an Implicit Commit”.

In MySQL 5.7.4 and later, the strict requirement to execute STOP SLAVE prior to issuing any CHANGE MASTER TO statement (and START SLAVE afterward) is removed. Instead of depending on whether the slave is stopped, the behavior of CHANGE MASTER TO depends (in MySQL 5.7.4 and later) on the states of the slave SQL thread and slave I/O threads; which of these threads is stopped or running now determines the options that can or cannot be used with a CHANGE MASTER TO statement at a given point in time. The rules for making this determination are listed here:

  • If the SQL thread is stopped, you can execute CHANGE MASTER TO using any combination that is otherwise allowed of RELAY_LOG_FILE, RELAY_LOG_POS, and MASTER_DELAY options, even if the slave I/O thread is running. No other options may be used with this statement when the I/O thread is running.

  • If the I/O thread is stopped, you can execute CHANGE MASTER TO using any of the options for this statement (in any allowed combination) except RELAY_LOG_FILE, RELAY_LOG_POS, or MASTER_DELAY, even when the SQL thread is running. These three options may not be used when the I/O thread is running.

  • Both the SQL thread and the I/O thread must be stopped before issuing a CHANGE MASTER TO statement that employs MASTER_AUTO_POSITION = 1.

You can check the current state of the slave SQL and I/O threads using SHOW SLAVE STATUS.

For more information, see Section 16.3.7, “Switching Masters During Failover”.

If you are using statement-based replication and temporary tables, it is possible for a CHANGE MASTER TO statement following a STOP SLAVE statement to leave behind temporary tables on the slave. In MySQL 5.7.4 and later, a warning (ER_WARN_OPEN_TEMP_TABLES_MUST_BE_ZERO) is now issued whenever this occurs. You can avoid this in such cases by making sure that the value of the Slave_open_temp_tables system status variable is equal to 0 prior to executing such a CHANGE MASTER TO statement.

CHANGE MASTER TO is useful for setting up a slave when you have the snapshot of the master and have recorded the master binary log coordinates corresponding to the time of the snapshot. After loading the snapshot into the slave to synchronize it with the master, you can run CHANGE MASTER TO MASTER_LOG_FILE='log_name', MASTER_LOG_POS=log_pos on the slave to specify the coordinates at which the slave should begin reading the master binary log.

The following example changes the master server the slave uses and establishes the master binary log coordinates from which the slave begins reading. This is used when you want to set up the slave to replicate the master:


The next example shows an operation that is less frequently employed. It is used when the slave has relay log files that you want it to execute again for some reason. To do this, the master need not be reachable. You need only use CHANGE MASTER TO and start the SQL thread (START SLAVE SQL_THREAD):


You can even use the second operation in a nonreplication setup with a standalone, nonslave server for recovery following a crash. Suppose that your server has crashed and you have restored it from a backup. You want to replay the server's own binary log files (not relay log files, but regular binary log files), named (for example) myhost-bin.*. First, make a backup copy of these binary log files in some safe place, in case you don't exactly follow the procedure below and accidentally have the server purge the binary log. Use SET GLOBAL relay_log_purge=0 for additional safety. Then start the server without the --log-bin option, Instead, use the --replicate-same-server-id, --relay-log=myhost-bin (to make the server believe that these regular binary log files are relay log files) and --skip-slave-start options. After the server starts, issue these statements:


The server reads and executes its own binary log files, thus achieving crash recovery. Once the recovery is finished, run STOP SLAVE, shut down the server, clear the master info and relay log info repositories, and restart the server with its original options.

Specifying the MASTER_HOST option (even with a dummy value) is required to make the server think it is a slave.

The following table shows the maximum permissible length for the string-valued options.

OptionMaximum Length

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