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    Data Transmission Service:Migrate data from an ApsaraDB RDS for MySQL instance to an ApsaraDB for ClickHouse cluster

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    Data Transmission Service:Migrate data from an ApsaraDB RDS for MySQL instance to an ApsaraDB for ClickHouse cluster

    Last Updated:Jun 06, 2025

    Data Transmission Service (DTS) allows you to migrate data from a self-managed MySQL database or an ApsaraDB RDS for MySQL instance to an ApsaraDB for ClickHouse cluster. This helps you analyze business data in a centralized manner. This topic use an ApsaraDB RDS for MySQL instance as an example to describe the data migration details.

    Prerequisites

    An ApsaraDB for ClickHouse cluster that runs ClickHouse V20.8 or later is created as the destination cluster. For more information, see Create an ApsaraDB for ClickHouse cluster.

    Note

    The available storage space of the destination ApsaraDB for ClickHouse cluster is larger than the total size of data in the source ApsaraDB RDS for MySQL instance.

    Usage notes

    Limits

    Description

    Limits on the source instance

    • If you select tables as the objects to be migrated and you need to edit the tables in the destination database, such as renaming tables or columns, up to 1,000 tables can be migrated in a single data migration task. If you run a task to migrate more than 1,000 tables, a request error occurs. In this case, we recommend that you configure multiple tasks to migrate the tables in batches or configure a task to migrate the entire database.

    • Binary logging:

      • By default, the binary logging feature is enabled for an ApsaraDB RDS for MySQL instance. Make sure that the binlog_row_image parameter is set to full. Otherwise, error messages are returned during the precheck and the data migration task cannot be started. For more information, see Modify instance parameters.

        Important

        • If the source database is a self-managed MySQL database, you must enable the binary logging feature and set the binlog_format parameter to row and the binlog_row_image parameter to full.

        • If the source database is a self-managed MySQL database deployed in a dual-primary cluster, you must set the log_slave_updates parameter to ON. This ensures that DTS can obtain all binary logs. For more information, see Create an account for a self-managed MySQL database and configure binary logging.

      • The binary logs of the source database must be stored for at least seven days. Otherwise, the data migration task may fail because DTS cannot obtain the binary logs. In exceptional circumstances, data inconsistency or loss may occur. Make sure that you configure the retention period of binary logs based on the preceding requirements. Otherwise, the service reliability or performance in the Service Level Agreement (SLA) of DTS may not be guaranteed. For more information about how to manage the binary log files of an ApsaraDB RDS for MySQL instance, see Manage binary log files.

    • In incremental data migration, an ApsaraDB RDS for MySQL instance that does not record transaction logs, such as a read-only ApsaraDB RDS for MySQL V5.6 instance, cannot be used as the source database.

    • Limits on operations to be performed on the source database:

      • During schema migration and full data migration, do not execute DDL statements to change the schemas of databases or tables. Otherwise, the data migration task fails.

      • If you perform only full data migration, do not write data to the source database during data migration. Otherwise, data inconsistency between the source and destination databases occurs. To ensure data consistency, we recommend that you select schema migration, full data migration, and incremental data migration as the migration types.

    • The data generated by change operation of binary logs, such as data restored from a physical backup or data from a cascade operation, is not recorded and migrated to the destination database when the data migration instance is running.

      Note

      If the change data is not recorded and migrated to the destination database, you can migrate full data again on the premise that your business is not affected.

    • If the source database is MySQL database 8.0.23 or later, and the data to be migrated includes invisible columns, the data of the columns cannot be obtained and data loss occurs.

      Note

      • To make the columns visible, run the ALTER TABLE <table_name> ALTER COLUMN <column_name> SET VISIBLE; command. For more information, see Invisible Columns.

      • Tables that do not have primary keys automatically generate invisible primary keys. You need to make the invisible primary keys visible. For more information, see Generated Invisible Primary Keys.

    Other limits

    • If the DDL statements executed in the source ApsaraDB RDS for MySQL instance are not in the standard MySQL syntax, the migration task may fail or data may be lost.

    • The RENAME TABLE operation cannot be migrated.

    • The DATETIME data in the source ApsaraDB RDS for MySQL instance must be in the time range supported by the destination ApsaraDB for ClickHouse cluster. Otherwise, data inconsistency between the source and destination databases occurs. For more information, see Time range.

    • All selected columns of the Partition Key parameter must be non-empty fields. Otherwise, the migration task fails.

    • Up to 256 databases can be migrated to an ApsaraDB for ClickHouse cluster.

    • The names of the databases, tables, and columns to be migrated must comply with the naming conventions of ApsaraDB for ClickHouse. For more information, see Limits on object naming conventions.

    • During schema migration, DTS adds the _sign, _is_deleted, and _version fields to destination tables. You must manually create a destination table to receive data and add these fields to the destination table if you do not select Schema Synchronization for Synchronization Types. For more information, see Tables and fields.

    • Before you migrate data, evaluate the impact of data migration on the performance of the source and destination databases. We recommend that you migration data during off-peak hours. During full data migration, DTS uses read and write resources of the source and destination databases. This may increase the loads on the database servers.

    • If you select one or more tables instead of an entire database as the objects to be migrated, do not use tools such as pt-online-schema-change to perform DDL operations on the tables during data migration. Otherwise, data may fail to be migrated.

      You can use Data Management (DMS) to perform online DDL operations. For more information, see Perform lock-free DDL operations.

    • Data inconsistency between the source and destination databases occurs if data from other sources is written to the destination database during data migration.

    • If the source database is an ApsaraDB RDS for MySQL instance for which the EncDB feature is enabled, full data migration cannot be performed.

      Note

      ApsaraDB RDS for MySQL instances that have the Transparent Data Encryption (TDE) feature enabled support schema migration, full data migration, and incremental data migration.

    • If a DTS task fails to run, DTS technical support will try to restore the task within 8 hours. During the restoration, the task may be restarted, and the parameters of the task may be modified.

      Note

      Only the parameters of the task may be modified. The parameters of databases are not modified. The parameters that may be modified include but are not limited to the parameters in the "Modify instance parameters" section of the Modify the parameters of a DTS instance topic.

    Special cases

    • If the source database is a self-managed MySQL database, take note of the following limits:

      • If you perform a primary/secondary switchover on the source database when the data migration task is running, the task fails.

      • DTS calculates migration latency based on the timestamp of the latest migrated data in the destination database and the current timestamp in the source database. If no DML operation is performed on the source database for a long time, the migration latency may be inaccurate. If the latency of the data migration task is excessively high, you can perform a DML operation on the source database to update the latency.

        Note

        If you select an entire database as the object to be migrated, you can create a heartbeat table. The heartbeat table is updated or receives data every second.

      • DTS executes the CREATE DATABASE IF NOT EXISTS `test` statement in the source database as scheduled to move forward the binary log file position.

    • If the source database is an Apsara RDS for MySQL instance, take note of the following limit:

      • In incremental data migration, an ApsaraDB RDS for MySQL instance that does not record transaction logs, such as a read-only ApsaraDB RDS for MySQL V5.6 instance, cannot be used as the source database.

      • DTS executes the CREATE DATABASE IF NOT EXISTS `test` statement in the source database as scheduled to move forward the binary log file position.

    Billing

    Migration type

    Task configuration fee

    Internet traffic fee

    Schema migration and full data migration

    Free of charge.

    Free of charge in this example.

    Incremental data migration

    Charged. For more information, see Billing overview.

    SQL operations that can be incrementally migrated

    Operation type

    SQL statement

    DML

    INSERT, UPDATE, DELETE

    DDL

    • CREATE TABLE

    • TRUNCATE TABLE

    • ALTER TABLE

    • ADD COLUMN

    • MODIFY COLUMN

    • DROP TABLE, DROP COLUMN

    Data type mappings

    The data types supported by Apsara RDS for MySQL instances and ApsaraDB for ClickHouse clusters do not have one-to-one correspondence. Therefore, DTS converts the data types of the source database to those of the destination database during initial schema migration. For more information, see Data type mappings between heterogeneous databases.

    Permissions required for database accounts

    Database

    Required permissions

    References

    Source ApsaraDB RDS for MySQL instance

    Read permissions on the objects to be migrated.

    Create an account and Modify account permissions.

    Destination ApsaraDB for ClickHouse cluster

    • ApsaraDB for ClickHouse V22.8 cluster and later: the read and write permissions on the destination database. In this case, you can use a privileged account.

    • ApsaraDB for ClickHouse V21.8 cluster: Read, Write and Set Permissions and Enable DDL.

    Manage database accounts in a Community-compatible Edition cluster

    Note

    If the source database account that you use is not created and authorized in the 

    ApsaraDB RDS for MySQL console, make sure that the account has the REPLICATION CLIENT, REPLICATION SLAVE, SHOW VIEW, and SELECT permissions.

    Procedure

    1. Use one of the following methods to go to the Data Migration page and select the region in which the data migration instance resides.

      DTS console

      1. Log on to the DTS console.

      2. In the left-side navigation pane, click Data Migration.

      3. In the upper-left corner of the page, select the region in which the data migration instance resides.

      DMS console

      Note

      The actual operation may vary based on the mode and layout of the DMS console. For more information, see Simple mode and Customize the layout and style of the DMS console.

      1. Log on to the DMS console.

      2. In the top navigation bar, move the pointer over Data + AI > DTS (DTS) > Data Migration.

      3. From the drop-down list to the right of Data Migration Tasks, select the region in which the data synchronization instance resides.

    2. Click Create Task to go to the task configuration page.

    3. Configure the source and destination databases. The following table describes the parameters.

      Section

      Parameter

      Description

      N/A

      Task Name

      The name of the DTS task. DTS automatically generates a task name. We recommend that you specify a descriptive name that makes it easy to identify the task. You do not need to specify a unique task name.

      Source Database

      Select Existing Connection

      • If you use a database instance that is registered with DTS, select the instance from the drop-down list. DTS automatically populates the following database parameters for the instance. For more information, see Manage database connections.

        Note

        In the DMS console, you can select the database instance from the Select a DMS database instance drop-down list.

      • If you fail to register the instance with DTS, or you do not need to use the instance that is registered with DTS, you must configure the following database information.

      Database Type

      The type of the source database. Select MySQL.

      Access Method

      The access method of the source database. Select Alibaba Cloud Instance.

      Instance Region

      The region in which the source c resides.

      Replicate Data Across Alibaba Cloud Accounts

      Specifies whether to migrate data across Alibaba Cloud accounts. In this example, No is selected.

      RDS Instance ID

      The ID of the source ApsaraDB RDS for MySQL instance.

      Database Account

      The database account of the source ApsaraDB RDS for MySQL instance. For more information about the permissions that are required for the account, see the Permissions required for database accounts section of this topic.

      Database Password

      The password that is used to access the database.

      Encryption

      Specifies whether to encrypt the connection to the database. You can select Non-encrypted or SSL-encrypted based on your business requirements. If you want to set this parameter to SSL-encrypted, you must enable SSL encryption for the ApsaraDB RDS for MySQL instance before you configure the DTS task. For more information, see Use a cloud certificate to enable SSL encryption.

      Destination Database

      Select Existing Connection

      • If you use a database instance that is registered with DTS, select the instance from the drop-down list. DTS automatically populates the following database parameters for the instance. For more information, see Manage database connections.

        Note

        In the DMS console, you can select the database instance from the Select a DMS database instance drop-down list.

      • If you fail to register the instance with DTS, or you do not need to use the instance that is registered with DTS, you must configure the following database information.

      Database Type

      The type of the destination database. Select ClickHouse.

      Access Method

      The access method of the destination database. Select Alibaba Cloud Instance.

      Instance Region

      The region in which the destination ApsaraDB for ClickHouse cluster resides.

      Replicate Data Across Alibaba Cloud Accounts

      Specifies whether to migrate data across Alibaba Cloud accounts. In this example, No is selected.

      Cluster Type

      The type of the destination ApsaraDB for ClickHouse cluster.

      Cluster ID

      The ID of the destination ApsaraDB for ClickHouse cluster.

      Database Account

      The database account of the destination ApsaraDB for ClickHouse cluster. For information about the permissions that are required for the account, see the Permissions required for database accounts section of this topic.

      Database Password

      The password that is used to access the database.

    4. In the lower part of the page, click Test Connectivity and Proceed.

      Note

      • Make sure that the CIDR blocks of DTS servers can be automatically or manually added to the security settings of the source and destination databases to allow access from DTS servers. For more information, see Add the CIDR blocks of DTS servers.

      • If the source or destination database is a self-managed database and its Access Method is not set to Alibaba Cloud Instance, click Test Connectivity in the CIDR Blocks of DTS Servers dialog box.

    5. Configure the objects to be migrated.

      1. On the Configure Objects page, configure the objects that you want to migrate.

        Parameter

        Description

        Migration Types

        • To perform only full data migration, select Schema Migration and Full Data Migration.

        • To ensure service continuity during data migration, select Schema Migration, Full Data Migration, and Incremental Data Migration.

        Note

        • If you do not select Schema Migration, make sure a database and a table are created in the destination database to receive data and the object name mapping feature is enabled in Selected Objects.

        • If you do not select Incremental Data Migration, we recommend that you do not write data to the source database during data migration. This ensures data consistency between the source and destination databases.

        Processing Mode of Conflicting Tables

        • Precheck and Report Errors: checks whether the destination database contains tables that use the same names as tables in the source database. If the source and destination databases do not contain tables that have identical table names, the precheck is passed. Otherwise, an error is returned during the precheck and the data migration task cannot be started.

          Note

          If the source and destination databases contain tables with identical names and the tables in the destination database cannot be deleted or renamed, you can use the object name mapping feature to rename the tables that are migrated to the destination database. For more information, see Map object names.

        • Ignore Errors and Proceed: skips the precheck for identical table names in the source and destination databases.

          Warning

          If you select Ignore Errors and Proceed, data inconsistency may occur and your business may be exposed to the following potential risks:

          • If the source and destination databases have the same schema, and a data record has the same primary key as an existing data record in the destination database, the following scenarios may occur:

            • During full data migration, DTS does not migrate the data record to the destination database. The existing data record in the destination database is retained.

            • During incremental data migration, DTS migrates the data record to the destination database. The existing data record in the destination database is overwritten.

          • If the source and destination databases have different schemas, only specific columns are migrated or the data migration task fails. Proceed with caution.

        Capitalization of Object Names in Destination Instance

        The capitalization of database names, table names, and column names in the destination instance. By default, DTS default policy is selected. You can select other options to make sure that the capitalization of object names is consistent with that of the source or destination database. For more information, see Specify the capitalization of object names in the destination instance.

        Source Objects

        Select one or more objects from the Source Objects section. Click the 向右小箭头 icon to add the objects to the Selected Objects section.

        Note

        You can select columns, tables, or databases as the objects to be migrated.

        Selected Objects

        • To rename an object that you want to migrate to the destination instance, right-click the object in the Selected Objects section. For more information, see Map the name of a single object.

        • To rename multiple objects at a time, click Batch Edit in the upper-right corner of the Selected Objects section. For more information, see Map multiple object names at a time.

        Note

        • To specify filter conditions to migrate data that meets specific conditions, right-click the table to be migrated in the Selected Objects section. In the dialog box that appears, specify one or more SQL conditions. For more information, see Set filter conditions.

        • If you use the object name mapping feature, other objects that depend on the renamed objects may fail to be migrated.

      2. Click Next: Advanced Settings to configure advanced settings.

        Parameter

        Description

        Dedicated Cluster for Task Scheduling

        By default, DTS schedules the data migration task to the shared cluster if you do not specify a dedicated cluster. If you want to improve the stability of data migration tasks, purchase a dedicated cluster. For more information, see What is a DTS dedicated cluster.

        Time zone of destination database

        The time zone of the date and time data type such as DateTime. You can select a time zone during the data synchronization to the destination ClickHouse cluster.

        Retry Time for Failed Connections

        The retry time range for failed connections. If the source or destination database fails to be connected after the data migration task is started, DTS immediately retries a connection within the retry time range. Valid values: 10 to 1,440. Unit: minutes. Default value: 720. We recommend that you set the parameter to a value greater than 30. If DTS is reconnected to the source and destination databases within the specified retry time range, DTS resumes the data migration task. Otherwise, the data migration task fails.

        Note

        • If you specify different retry time ranges for multiple data migration tasks that share the same source or destination database, the value that is specified later takes precedence.

        • When DTS retries a connection, you are charged for the DTS instance. We recommend that you specify the retry time range based on your business requirements. You can also release the DTS instance at the earliest opportunity after the source database and destination instance are released.

        Retry Time for Other Issues

        The retry time range for other issues. For example, if DDL or DML operations fail to be performed after the data migration task is started, DTS immediately retries the operations within the retry time range. Valid values: 1 to 1440. Unit: minutes. Default value: 10. We recommend that you set the parameter to a value greater than 10. If the failed operations are successfully performed within the specified retry time range, DTS resumes the data migration task. Otherwise, the data migration task fails.

        Important

        The value of the Retry Time for Other Issues parameter must be smaller than the value of the Retry Time for Failed Connections parameter.

        Enable Throttling for Full Data Migration

        Specifies whether to enable throttling for full data migration. During full data migration, DTS uses the read and write resources of the source and destination databases. This may increase the loads of the database servers. You can enable throttling for full data migration based on your business requirements. To configure throttling, you must configure the Queries per second (QPS) to the source database, RPS of Full Data Migration, and Data migration speed for full migration (MB/s) parameters. This reduces the loads of the destination database server.

        Note

        You can configure this parameter only if you select Full Data Migration for the Migration Types parameter.

        Enable Throttling for Incremental Data Migration

        Specifies whether to enable throttling for incremental data migration. To configure throttling, you must configure the RPS of Incremental Data Migration and Data migration speed for incremental migration (MB/s) parameters. This reduces the loads of the destination database server.

        Note

        You can configure this parameter only if you select Incremental Data Migration for the Migration Types parameter.

        Whether to delete SQL operations on heartbeat tables of forward and reverse tasks

        Specifies whether to write SQL operations on heartbeat tables to the source database while the DTS instance is running. Valid values:

        • Yes: does not write SQL operations on heartbeat tables. In this case, a latency of the DTS instance may be displayed.

        • No: writes SQL operations on heartbeat tables. In this case, features such as physical backup and cloning of the source database may be affected.

        Environment Tag

        The environment tag that is used to identify the DTS instance. You can select an environment tag based on your business requirements. In this example, no environment tag is selected.

        Configure ETL

        Specifies whether to enable the extract, transform, and load (ETL) feature. For more information, see What is ETL? Valid values:

        Monitoring and Alerting

        Specifies whether to configure alerting for the data migration task. If the task fails or the migration latency exceeds the specified threshold, the alert contacts receive notifications. Valid values:

      3. Click Next: Configure Database and Table Fields and then configure the Type, Primary Key Column, Sort Key, Distribution Key, and Partition Key parameters for the table that is migrated.

        Note

        • By default, the parameters are configured by DTS. To modify the parameters, set the Definition Status parameter to All.

        • You can select multiple columns for the Primary Key Column or Sort Key parameter from the corresponding drop-down list. One or more columns specified for the Primary Key Column parameter can be selected for the Partition Key parameter. You can select only one column for the Distribution Key parameter. For more information, see CREATE TABLE.

        • You can leave the Partition Key parameter empty, but you cannot select a field that contains no data for this parameter. Otherwise, the data migration task fails.

    6. Save the task settings and run a precheck.

      • To view the parameters to be specified when you call the relevant API operation to configure the DTS task, move the pointer over Next: Save Task Settings and Precheck and click Preview OpenAPI parameters.

      • If you do not need to view or have viewed the parameters, click Next: Save Task Settings and Precheck in the lower part of the page.

      Note

      • Before you can start the data migration task, DTS performs a precheck. You can start the data migration task only after the task passes the precheck.

      • If the task fails to pass the precheck, click View Details next to each failed item. After you analyze the causes based on the check results, troubleshoot the issues. Then, run a precheck again.

      • If an alert is triggered for an item during the precheck:

        • If an alert item cannot be ignored, click View Details next to the failed item and troubleshoot the issues. Then, run a precheck again.

        • If the alert item can be ignored, click Confirm Alert Details. In the View Details dialog box, click Ignore. In the message that appears, click OK. Then, click Precheck Again to run a precheck again. If you ignore the alert item, data inconsistency may occur, and your business may be exposed to potential risks.

    7. Purchase an instance.

      1. Wait until Success Rate becomes 100%. Then, click Next: Purchase Instance.

      2. On the Purchase Instance page, configure the Instance Class parameter for the data migration instance. The following table describes the parameters.

        Section

        Parameter

        Description

        New Instance Class

        Resource Group

        The resource group to which the data migration instance belongs. Default value: default resource group. For more information, see What is Resource Management?

        Instance Class

        DTS provides instance classes that vary in the migration speed. You can select an instance class based on your business scenario. For more information, see Instance classes of data migration instances.

      3. Read and agree to Data Transmission Service (Pay-as-you-go) Service Terms by selecting the check box.

      4. Click Buy and Start. In the message that appears, click OK.

        You can view the progress of the task on the Data Migration page.

        Note

        • If a data migration task cannot be used to migrate incremental data, the task automatically stops. The Completed is displayed in the Status section.

        • If a data migration task can be used to migrate incremental data, the task does not automatically stop. The incremental data migration task never stops or completes. The Running is displayed in the Status section.

    Appendix

    Time range

    Data type

    Minimum value

    Maximum value

    Date

    1970-01-01 00:00:00

    2149-06-06 00:00:00

    Date32

    1925-01-01 00:00:00

    2283-11-11 00:00:00

    DateTime

    1970-01-01 08:00:00

    2106-02-07 14:28:15

    DateTime64

    1925-01-01 08:00:00

    2283-11-12 07:59:59

    Tables and fields

    Tables

    If you do not use the object name mapping feature, make sure that the tables you create meet the following requirements:

    Important

    If a destination table contains the ENGINE parameter, the parameter must be set to ENGINE = ReplicatedReplacingMergeTree(_version, _is_deleted). Otherwise, data inconsistency may occur.

    • If the destination database is an ApsaraDB for ClickHouse Community-compatible Edition cluster, you must create a local table and a distributed table. The name of the distributed table must be the same as that of the source table. The name of the local table is in the <Distributed table name>_local format.

    • If the destination database is an ApsaraDB for ClickHouse Enterprise Edition cluster, you must create a table with the same name as the source table.

    Fields

    Note

    You can execute the select * from table_name final where _sign>0; statement to query data that is synchronized to an ApsaraDB for ClickHouse cluster. In this statement, the WHERE clause can be used to filter the deleted data, and the final field behind the table name can be used to filter the data with the same sort keys.

    Version

    Field

    Data type

    Default value

    Description

    ApsaraDB for ClickHouse Community-compatible Edition cluster that runs ClickHouse V23.8 or earlier

    _sign

    Int8

    1

    The type of the DML operation. Valid values:

    • INSERT: 1.

    • UPDATE: 1.

    • DELETE: -1.

    _version

    UInt64

    1

    The time when data is written to the ClickHouse cluster.

    ApsaraDB for ClickHouse Enterprise Edition cluster or ApsaraDB for ClickHouse Community-compatible Edition cluster that runs CLickHouse V23.8 or later

    _sign

    Int8

    1

    The type of the DML operation. Valid values:

    • INSERT: 1.

    • UPDATE: 1.

    • DELETE: -1.

    _is_deleted

    UInt8

    0

    Specifies whether the data record is deleted. Valid values:

    • Insert: 0.

    • Delete: 1.

    • Update: 0.

    _version

    UInt64

    1

    The timestamp when data is written to the ClickHouse cluster.