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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'
  | MASTER_PUBLIC_KEY_PATH = 'key_file_name'
  | 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 17.2.4, “Replication Relay and Status Logs”). CHANGE MASTER TO requires the REPLICATION_SLAVE_ADMIN or SUPER privilege.

You can issue CHANGE MASTER TO statements on a running slave without first stopping it, 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 multithreaded 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 17.2.3, “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.

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. Trying to set MASTER_HOST to an empty string fails with an error.

    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; trying to use a password of more than 32 characters causes CHANGE MASTER TO to fail.

    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, and the MASTER_TLS_VERSION option, specify how the slave uses encryption and ciphers to secure the replication connection. 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. The MASTER_SSL_xxx options perform the same functions as the --ssl-xxx options described in Section 6.4.2, “Command Options for Encrypted Connections”. The correspondence between the two sets of options, and the use of the MASTER_SSL_xxx and MASTER_TLS_VERSION options to set up a secure connection, is explained in Section 17.3.9, “Setting Up Replication to Use Encrypted Connections”.


To connect to the replication master using a user account that authenticates with the caching_sha2_password plugin, you must either set up a secure connection as described in Section 17.3.9, “Setting Up Replication to Use Encrypted Connections”, or enable the unencrypted connection to support password exchange using an RSA key pair. The caching_sha2_password authentication plugin is the default for new users created from MySQL 8.0 (for details, see Section, “Caching SHA-2 Pluggable Authentication”). If the user account that you create or use for replication (as specified by the MASTER_USER option) uses this authentication plugin, and you are not using a secure connection, you must enable RSA key pair-based password exchange for a successful connection.

To enable RSA key pair-based password exchange, specify either the MASTER_PUBLIC_KEY_PATH or the GET_MASTER_PUBLIC_KEY=1 option. Either of these options provides the RSA public key to the slave:

  • MASTER_PUBLIC_KEY_PATH indicates the path name to a file containing a slave-side copy of the public key required by the master for RSA key pair-based password exchange. The file must be in PEM format. This option applies to slaves that authenticate with the sha256_password or caching_sha2_password authentication plugin. (For sha256_password, MASTER_PUBLIC_KEY_PATH can be used only if MySQL was built using OpenSSL.)

  • GET_MASTER_PUBLIC_KEY indicates whether to request from the master the public key required for RSA key pair-based password exchange. This option applies to slaves that authenticate with the caching_sha2_password authentication plugin. For connections by accounts that authenticate using this plugin, the master does not send the public key unless requested, so it must be requested or specified in the client. If MASTER_PUBLIC_KEY_PATH is given and specifies a valid public key file, it takes precedence over GET_MASTER_PUBLIC_KEY.

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 from versions earlier than MySQL 5.6, 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 17.3.11, “Delayed Replication”.

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. In the master info repository table mysql.slave_master_info, the value can be seen as the Master_bind column.

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. 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.

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. 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. Since the GTID of the last transmitted transaction is included in Retrieved_gtid_set even if the transaction was only partially transmitted, the last received GTID is subtracted from this set. Thus, the slave computes 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.

You can see whether replication is running with autopositioning enabled by checking the output of SHOW SLAVE STATUS.

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_POSITION.

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 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.


When global transaction identifiers (GTIDs) are used for replication, transactions that have already been applied are automatically ignored, so the IGNORE_SERVER_IDS function is not required and is deprecated. If gtid_mode=ON is set for the server, a deprecation warning is issued if you include the IGNORE_SERVER_IDS option in a CHANGE MASTER TO statement.

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”.

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:




A deprecation warning is issued if SET GTID_MODE=ON is issued when any channel has existing server IDs set with IGNORE_SERVER_IDS. Before starting GTID-based replication, check for and clear all ignored server ID lists on the servers involved. The SHOW_SLAVE_STATUS statement displays the list of ignored IDs, if there is one. If you do receive the deprecation warning, you can still clear a list after gtid_mode=ON is set by issuing a CHANGE MASTER TO statement containing the IGNORE_SERVER_IDS option with an empty list.

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.

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

From MySQL 5.7, 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 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 17.3.8, “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. 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.

Option Maximum Length

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