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Excerpts from this Manual CHANGE MASTER TO Statement

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

option: {
    MASTER_BIND = 'interface_name'
  | MASTER_HOST = 'host_name'
  | MASTER_USER = 'user_name'
  | MASTER_PASSWORD = 'password'
  | MASTER_PORT = port_num
  | PRIVILEGE_CHECKS_USER = {'account' | NULL}
  | MASTER_LOG_FILE = 'source_log_name'
  | MASTER_LOG_POS = source_log_pos
  | RELAY_LOG_FILE = 'relay_log_name'
  | RELAY_LOG_POS = relay_log_pos
  | MASTER_DELAY = interval
  | 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_TLS_CIPHERSUITES = 'ciphersuite_list'
  | MASTER_PUBLIC_KEY_PATH = 'key_file_name'
  | NETWORK_NAMESPACE = 'namespace'
  | IGNORE_SERVER_IDS = (server_id_list)

    FOR CHANNEL channel

    [server_id [, server_id] ... ]

CHANGE MASTER TO changes the parameters that the replica server uses for connecting to the source, for reading the source's binary log, and reading the replica's relay log. It also updates the contents of the replication metadata repositories (see Section 17.2.4, “Relay Log and Replication Metadata Repositories”). CHANGE MASTER TO requires the REPLICATION_SLAVE_ADMIN privilege (or the deprecated SUPER privilege).

You can issue CHANGE MASTER TO statements on a running replica without first stopping it, depending on the states of the replication SQL thread and replication I/O thread. The rules governing such use are provided later in this section.

When using a multithreaded replica (in other words slave_parallel_workers is greater than 0), stopping the replica can cause gaps in the sequence of transactions that have been executed from the relay log, regardless of whether the replica was stopped intentionally or otherwise. When such gaps exist, issuing CHANGE MASTER TO fails. The solution in this situation is to issue START REPLICA | 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 17.2.2, “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, MASTER_PORT, and NETWORK_NAMESPACE provide information to the replica about how to connect to its source:

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


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

    If you specify the MASTER_HOST or MASTER_PORT option, the replica assumes that the source 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 source's 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 replication user account to use for connecting to the source. If you specify MASTER_PASSWORD, MASTER_USER is also required. The password used for a replication user 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.

    It is possible to set an empty user name by specifying MASTER_USER='', but the replication channel cannot be started with an empty user name. In releases before MySQL 8.0.21, only set an empty MASTER_USER user name if you need to clear previously used credentials from the replication metadata repositories for security purposes. Do not use the channel afterwards, due to a bug in these releases that can substitute a default user name if an empty user name is read from the repositories (for example, during an automatic restart of a Group Replication channel). From MySQL 8.0.21, it is valid to set an empty MASTER_USER user name and use the channel afterwards if you always provide user credentials using the START REPLICA | SLAVE statement or START GROUP_REPLICATION statement that starts the replication channel. This approach means that the replication channel always needs operator intervention to restart, but the user credentials are not recorded in the replication metadata repositories.

    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 REPLICA | SLAVE statement is also visible to SHOW PROCESSLIST.)

  • NETWORK_NAMESPACE specifies the network namespace to use for TCP/IP connections to the source. If this option is omitted, connections from the replica use the default (global) namespace.

    For information about network namespaces, see Section 5.1.14, “Network Namespace Support”.

    This option was added in MySQL 8.0.22. On platforms that do not implement network namespace support, failure occurs when the replica attempts to connect to the source.

REQUIRE_ROW_FORMAT (available as of MySQL 8.0.19) permits only row-based replication events to be processed by the replication channel. This option prevents the replication applier from taking actions such as creating temporary tables and executing LOAD DATA INFILE requests, which increases the security of the channel. Group Replication channels are automatically created with REQUIRE_ROW_FORMAT set, and you cannot change the option for those channels. For more information, see Section 17.3.3, “Replication Privilege Checks”.

PRIVILEGE_CHECKS_USER (available as of MySQL 8.0.18) names a user account that supplies a security context for the specified channel. NULL, which is the default, means no security context is used. The use of row-based binary logging is strongly recommended when PRIVILEGE_CHECKS_USER is set, and you can set REQUIRE_ROW_FORMAT to enforce this. For example, to start privilege checks on the channel channel_1 on a running replica, issue the following statements:

mysql> STOP REPLICA | SLAVE FOR CHANNEL 'channel_1';
         PRIVILEGE_CHECKS_USER = 'priv_repl'@'',
         REQUIRE_ROW_FORMAT = 1,
         FOR CHANNEL 'channel_1';

The user name and host name for the user account must follow the syntax described in Section 6.2.4, “Specifying Account Names”, and the user must not be an anonymous user (with a blank user name) or the CURRENT_USER. The account must have the REPLICATION_APPLIER privilege, plus the required privileges to execute the transactions replicated on the channel. For details of the privileges required by the account, see Section 17.3.3, “Replication Privilege Checks”. When you restart the replication channel, the privilege checks are applied from that point on. If you do not specify a channel and no other channels exist, the statement is applied to the default channel.

REQUIRE_TABLE_PRIMARY_KEY_CHECK (available as of MySQL 8.0.20) enables a replica to select its own policy for primary key checks. When the option is set to ON for a replication channel, the replica always uses the value ON for the sql_require_primary_key system variable in replication operations, requiring a primary key. When the option is set to OFF, the replica always uses the value OFF for the sql_require_primary_key system variable in replication operations, so that a primary key is never required, even if the source required one. When the REQUIRE_TABLE_PRIMARY_KEY_CHECK option is set to STREAM, which is the default, the replica uses whatever value is replicated from the source for each transaction.

  • For multisource replication, setting REQUIRE_TABLE_PRIMARY_KEY_CHECK to ON or OFF enables a replica to normalize behavior across the replication channels for different sources, and keep a consistent setting for the sql_require_primary_key system variable. Using ON safeguards against the accidental loss of primary keys when multiple sources update the same set of tables. Using OFF allows sources that can manipulate primary keys to work alongside sources that cannot.

  • When PRIVILEGE_CHECKS_USER is set, setting REQUIRE_TABLE_PRIMARY_KEY_CHECK to ON or OFF means that the user account does not need session administration level privileges to set restricted session variables, which are required to change the value of sql_require_primary_key to match the source's setting for each transaction. For more information, see Section 17.3.3, “Replication Privilege Checks”.

MASTER_COMPRESSION_ALGORITHMS and MASTER_ZSTD_COMPRESSION_LEVEL (available as of MySQL 8.0.18) enable control over the use of compression for connections to the source:

  • MASTER_COMPRESSION_ALGORITHMS specifies the permitted compression algorithms. The available algorithms are the same as for the protocol_compression_algorithms system variable. The default value is uncompressed.

    The value of MASTER_COMPRESSION_ALGORITHMS applies only if the slave_compressed_protocol system variable is disabled. If slave_compressed_protocol is enabled, it takes precedence over MASTER_COMPRESSION_ALGORITHMS and connections to the source use zlib compression if both source and replica support that algorithm.

  • MASTER_ZSTD_COMPRESSION_LEVEL is the compression level to use for connections that use the zstd compression algorithm. The permitted levels are from 1 to 22, with larger values indicating increasing levels of compression. The default zstd compression level is 3. The compression level setting has no effect on connections that do not use zstd compression.

For more information, see Section 4.2.8, “Connection Compression Control”.

Binary log transaction compression (available as of MySQL 8.0.20), which is activated by the binlog_transaction_compression system variable, can also be used to save bandwidth. If you do this in combination with connection compression, connection compression has less opportunity to act on the data, but can still compress headers and those events and transaction payloads that are uncompressed. For more information on binary log transaction compression, see Section, “Binary Log Transaction Compression”.

The MASTER_SSL_xxx options and the MASTER_TLS_xxx options specify how the replica uses encryption and ciphers to secure the replication connection. These options can be changed even on replicas that are compiled without SSL support. They are saved to the source metadata repository, but are ignored if the replica does not have SSL support enabled. The MASTER_SSL_xxx and MASTER_TLS_xxx options perform the same functions as the --ssl-xxx and --tls-xxx client options described in Command Options for Encrypted Connections. The correspondence between the two sets of options, and the use of the MASTER_SSL_xxx and MASTER_TLS_xxx options to set up a secure connection, is explained in Section 17.3.1, “Setting Up Replication to Use Encrypted Connections”.


To connect to the source using a replication user account that authenticates with the caching_sha2_password plugin, you must either set up a secure connection as described in Section 17.3.1, “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 replica:

  • MASTER_PUBLIC_KEY_PATH indicates the path name to a file containing a replica-side copy of the public key required by the source for RSA key pair-based password exchange. The file must be in PEM format. This option applies to replicas 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 source the public key required for RSA key pair-based password exchange. This option applies to replicas that authenticate with the caching_sha2_password authentication plugin. For connections by accounts that authenticate using this plugin, the source 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.

The MASTER_HEARTBEAT_PERIOD, MASTER_CONNECT_RETRY, MASTER_RETRY_COUNT , and (from MySQL 8.0.22) SOURCE_CONNECTION_AUTO_FAILOVER options control how the replica recognizes that the connection to the source has been lost and makes attempts to reconnect.

  • The slave_net_timeout system variable specifies the number of seconds that the replica waits for either more data or a heartbeat signal from the source, before the replica considers the connection broken, aborts the read, and tries to reconnect. The default value is 60 seconds (one minute).

  • The heartbeat interval, which stops the connection timeout occurring in the absence of data if the connection is still good, is controlled by the MASTER_HEARTBEAT_PERIOD option. A heartbeat signal is sent to the replica after that number of seconds, and the waiting period is reset whenever the source's binary log is updated with an event. Heartbeats are therefore sent by the source only if there are no unsent events in the binary log file for a period longer than this. The heartbeat interval interval is a decimal value having the range 0 to 4294967 seconds and a resolution in milliseconds; the smallest nonzero value is 0.001. Setting interval to 0 disables heartbeats altogether. The heartbeat interval defaults to half the value of the slave_net_timeout system variable. It is recorded in the source metadata repository and shown in the replication_connection_configuration Performance Schema table. Issuing RESET REPLICA | SLAVE resets the heartbeat interval to the default value.

    Note that a change to the value or default setting of slave_net_timeout does not automatically change the heartbeat interval, whether that has been set explicitly or is using a previously calculated default. A warning is issued if you set @@GLOBAL.slave_net_timeout to a value less than that of the current heartbeat interval. If slave_net_timeout is changed, you must also issue CHANGE MASTER TO to adjust the heartbeat interval to an appropriate value so that the heartbeat signal occurs before the connection timeout. If you do not do this, the heartbeat signal has no effect, and if no data is received from the source, the replica can make repeated reconnection attempts, creating zombie dump threads.

  • If the replica does need to reconnect, the first retry occurs immediately after the timeout. MASTER_CONNECT_RETRY specifies the interval between reconnection attempts, and MASTER_RETRY_COUNT limits the number of reconnection attempts. If both the default settings are used, the replica waits 60 seconds between reconnection attempts (MASTER_CONNECT_RETRY=60), and keeps attempting to reconnect at this rate for 60 days (MASTER_RETRY_COUNT=86400). These values are recorded in the source metadata repository and shown in the replication_connection_configuration Performance Schema table. MASTER_RETRY_COUNT supersedes the --master-retry-count server startup option.

  • From MySQL 8.0.22, you can set the SOURCE_CONNECTION_AUTO_FAILOVER option to activate the asynchronous connection failover mechanism for a replication channel if one or more alternative replication source servers are available (so when there are multiple MySQL servers or groups of servers that share the replicated data). The asynchronous connection failover mechanism takes over after the reconnection attempts controlled by MASTER_CONNECT_RETRY and MASTER_RETRY_COUNT are exhausted. It reconnects the replica to an alternative source chosen from a specified source list, which you manage using the asynchronous_connection_failover_add_source and asynchronous_connection_failover_delete_source UDFs.

    1. You can only set SOURCE_CONNECTION_AUTO_FAILOVER = 1 when GTID auto-positioning is in use (MASTER_AUTO_POSITION = 1).

    2. When you set SOURCE_CONNECTION_AUTO_FAILOVER = 1, set MASTER_RETRY_COUNT to a minimal number that just allows a few retry attempts with the same source, in case the connection failure is caused by a transient network outage. Otherwise the asynchronous connection failover mechanism cannot be activated promptly.

    3. When you set SOURCE_CONNECTION_AUTO_FAILOVER = 1, the replication metadata repositories must contain the credentials for a replication user account that can be used to connect to all the servers on the source list for the replication channel. These credentials can be set using the CHANGE MASTER TO statement with the MASTER_USER and MASTER_PASSWORD options.

MASTER_DELAY specifies how many seconds behind the source the replica must lag. An event received from the source is not executed until at least interval seconds later than its execution on the source. 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 17.4.11, “Delayed Replication”. A CHANGE MASTER TO statement employing the MASTER_DELAY option can be executed on a running replica when the replication SQL thread is stopped.

MASTER_BIND is for use on replicas that have multiple network interfaces, and determines which of the replica's network interfaces is chosen for connecting to the source. The address configured with this option, if any, can be seen in the Master_Bind column of the output from SHOW REPLICA | SLAVE STATUS. In the source metadata repository table mysql.slave_master_info, the value can be seen as the Master_bind column. The ability to bind a replica to a specific network interface is also supported by NDB Cluster.

MASTER_LOG_FILE and MASTER_LOG_POS are the coordinates at which the replication I/O thread should begin reading from the source the next time the thread starts. RELAY_LOG_FILE and RELAY_LOG_POS are the coordinates at which the replication 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 replica uses the last coordinates of the replication SQL thread before CHANGE MASTER TO was issued. This ensures that there is no discontinuity in replication, even if the replication SQL thread was late compared to the replication I/O thread, when you merely want to change, say, the password to use.

RELAY_LOG_FILE can use either an absolute or relative path, and uses the same base name as MASTER_LOG_FILE. A CHANGE MASTER TO statement employing RELAY_LOG_FILE, RELAY_LOG_POS, or both options can be executed on a running replica when the replication SQL thread is stopped. Relay logs are preserved if at least one of the replication SQL thread and the replication 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. Note that the Group Replication applier channel (group_replication_applier) has no I/O thread, only a SQL thread. For this channel, the relay logs are not preserved when the SQL thread is stopped.

When MASTER_AUTO_POSITION = 1 is used with CHANGE MASTER TO, the replica attempts to connect to the source using the GTID-based replication protocol. This option can be used with CHANGE MASTER TO only if both the replication SQL thread and replication I/O thread are stopped. Both the replica and the source must have GTIDs enabled (GTID_MODE=ON, ON_PERMISSIVE, or OFF_PERMISSIVE on the replica, and GTID_MODE=ON on the source). Auto-positioning is used for the connection, so the coordinates represented by MASTER_LOG_FILE and MASTER_LOG_POS are not used, and the use of either or both of these options together with MASTER_AUTO_POSITION = 1 causes an error. If multi-source replication is enabled on the replica, you need to set the MASTER_AUTO_POSITION = 1 option for each applicable replication channel.

With MASTER_AUTO_POSITION = 1 set, in the initial connection handshake, the replica sends a GTID set containing the transactions that it has already received, committed, or both. The source responds by sending all transactions recorded in its binary log whose GTID is not included in the GTID set sent by the replica. This exchange ensures that the source only sends the transactions with a GTID that the replica has not already recorded or committed. If the replica receives transactions from more than one source, as in the case of a diamond topology, the auto-skip function ensures that the transactions are not applied twice. For details of how the GTID set sent by the replica is computed, see Section, “GTID Auto-Positioning”.

If any of the transactions that should be sent by the source have been purged from the source's binary log, or added to the set of GTIDs in the gtid_purged system variable by another method, the source sends the error ER_MASTER_HAS_PURGED_REQUIRED_GTIDS to the replica, and replication does not start. The GTIDs of the missing purged transactions are identified and listed in the source's error log in the warning message ER_FOUND_MISSING_GTIDS. Also, if during the exchange of transactions it is found that the replica has recorded or committed transactions with the source's UUID in the GTID, but the source itself has not committed them, the source sends the error ER_SLAVE_HAS_MORE_GTIDS_THAN_MASTER to the replica and replication does not start. For information on how to handle these situations, see Section, “GTID Auto-Positioning”.

You can see whether replication is running with auto-positioning enabled by checking the Performance Schema replication_connection_status table or the output of SHOW REPLICA | SLAVE STATUS. Disabling the MASTER_AUTO_POSITION option again makes the replica revert to file-based replication, in which case you must also specify one or both of the MASTER_LOG_FILE or MASTER_LOG_POS options.

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 source 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 source metadata repository and the output of SHOW REPLICA | SLAVE STATUS provide the list of servers that are currently ignored. For more information, see Section, “Replication Metadata Repositories”, and Section, “SHOW REPLICA | SLAVE STATUS Statement”.

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 REPLICA | 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 replica'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 REPLICA | SLAVE prior to issuing any CHANGE MASTER TO statement (and START REPLICA | SLAVE afterward) is removed. Instead of depending on whether the replica is stopped, the behavior of CHANGE MASTER TO depends on the states of the replication SQL thread and replication I/O thread; 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 replication 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, MASTER_DELAY, or MASTER_AUTO_POSITION = 1 even when the SQL 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 replication SQL thread and replication I/O thread using SHOW REPLICA | SLAVE STATUS. Note that the Group Replication applier channel (group_replication_applier) has no I/O thread, only a SQL thread.

For more information, see Section 17.4.8, “Switching Sources During Failover”.

If you are using statement-based replication and temporary tables, it is possible for a CHANGE MASTER TO statement following a STOP REPLICA | SLAVE statement to leave behind temporary tables on the replica. 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 replica when you have the snapshot of the source and have recorded the source's binary log coordinates corresponding to the time of the snapshot. After loading the snapshot into the replica to synchronize it with the source, you can run CHANGE MASTER TO MASTER_LOG_FILE='log_name', MASTER_LOG_POS=log_pos on the replica to specify the coordinates at which the replica should begin reading the source's binary log.

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


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


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

Option Maximum Length
MASTER_HOST 255 (60 prior to MySQL 8.0.17)