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    Data Transmission Service:Migrate PolarDB for MySQL to DataHub

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    Data Transmission Service:Migrate PolarDB for MySQL to DataHub

    Last Updated:Jun 18, 2026

    Use Data Transmission Service (DTS) to migrate data from a PolarDB for MySQL cluster to a DataHub project.

    Prerequisites

    • You have created a destination DataHub project. For more information, see Quick start.

    • DataHub has been activated, and a project has been created to receive the migrated data. For more information, see Quick start and Manage projects.

    • The destination DataHub project must have more storage space than the source PolarDB for MySQL cluster currently uses.

    Limitations

    Note

    DTS does not migrate foreign keys from the source database to the destination database. Therefore, operations such as cascade delete in the source database are not migrated to the destination database.

    Category

    Description

    Source database limitations

    • Bandwidth requirements: The server that hosts the source database must have sufficient outbound bandwidth. Otherwise, the data migration speed will be affected.

    • The tables to be migrated must have a primary key or a unique constraint, and the values in the columns must be unique. Otherwise, duplicate data may appear in the destination database.

    • If you migrate data at the table level and need to perform edits such as column mapping, a single data migration task supports a maximum of 1,000 tables. To migrate more tables, we recommend splitting them into multiple tasks or configuring a task to migrate the entire database. Otherwise, a request error may occur after you submit the task.

    • If you perform incremental migration:

      • You must enable binary logging and set the loose_polar_log_bin parameter to on. Otherwise, the precheck reports an error and the data migration task cannot start. For more information about how to enable binary logging and modify parameters, see Enable binary logging and Modify parameters.

        Note

        Enabling binary logging for a PolarDB for MySQL cluster consumes storage space and incurs storage fees.

      • The binary logs of the PolarDB for MySQL cluster must be retained for at least 3 days. We recommend a retention period of 7 days. Otherwise, DTS may fail to obtain the binary logs, which can cause the task to fail. In extreme cases, this can lead to data inconsistency or data loss. Issues caused by a binary log retention period shorter than the DTS requirement are not covered by the DTS Service-Level Agreement (SLA).

        Note

        For more information about how to set the retention period for binary logs of a PolarDB for MySQL cluster, see Modify the retention period.

    • Do not perform DDL operations that change the schema of a database or table during schema migration. Otherwise, the data migration task fails.

    Other limitations

    • A single String field in DataHub can be up to 2 MB in length.

    • Only table-level data migration is supported. If you add a column to a source table that is being migrated, the data in that new column will not be migrated.

    • DTS cannot migrate read-only nodes of a source PolarDB for MySQL cluster.

    • DTS does not support the migration of OSS external tables from the source PolarDB for MySQL instance.

    • DTS does not support primary/standby switchover scenarios for the database instance during full data migration. In such a scenario, reconfigure the migration task promptly.

    • Full data migration consumes read and write resources on the source and destination databases, which can increase their load. We recommend evaluating the performance of both databases and performing the migration during off-peak hours.

    • For columns of the FLOAT or DOUBLE data type, DTS uses ROUND(COLUMN,PRECISION) to read values. If you do not explicitly define the precision, DTS uses a default migration precision of 38 digits for FLOAT and 308 digits for DOUBLE. Make sure the precision meets your requirements.

    • DTS attempts to resume a failed migration task within seven days. Before you perform a workload switchover to the destination instance, you must stop or release the migration instance. Alternatively, you can run the REVOKE command to revoke the write permissions from the account that DTS uses to access the destination instance. This prevents the task from automatically resuming and overwriting data in the destination instance.

    • Do not use tools such as pt-online-schema-change to perform online DDL operations on migration objects in the source database. Otherwise, the migration fails.

    • If a task fails, DTS support staff will attempt to restore it within eight hours. During restoration, they may restart the task or adjust its parameters.

      Note

      Only DTS task parameters are modified—not database parameters. Parameters that may be adjusted include those listed in Modify instance parameters.

    Other notes

    DTS periodically runs the CREATE DATABASE IF NOT EXISTS test command on the source database to advance the binary log position.

    Billing

    Migration type

    Instance configuration fee

    Internet traffic fee

    Schema migration and full data migration

    Free of charge.

    When the Access Method parameter of the destination database is set to Public IP Address, you are charged for Internet traffic. For more information, see Billing overview.

    Incremental data migration

    Charged. For more information, see Billing overview.

    Migration types

    • Schema migration

      DTS migrates the schema definitions of the migration objects from the source database to the destination database.

    • Incremental migration

      After a full migration is complete, DTS migrates incremental data updates from the source database to the destination database. Incremental migration lets you smoothly migrate data without interrupting your self-managed applications.

    SQL operations for incremental migration

    Operation type

    SQL statement

    DML

    INSERT, UPDATE, DELETE

    DDL

    ADD COLUMN

    Important

    If you manually modify the table structure in the target database, restart the task: pause and then start the task.

    Permissions required for database accounts

    Database

    Required permissions

    Account and permissions

    PolarDB for MySQL cluster

    Read permissions on migration objects

    Create and manage database accounts

    Procedure

    1. Navigate to the migration task list page for the destination region using one of the following methods.

      From the DTS console

      1. Log on to the Data Transmission Service (DTS) console.

      2. In the navigation pane on the left, click Data Migration.

      3. In the upper-left corner of the page, select the region where the migration instance is located.

      From the DMS console

      Note

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

      1. Log on to the Data Management (DMS) console.

      2. In the top menu bar, choose Data + AI > Data Transmission (DTS) > Data Migration.

      3. To the right of Data Migration Tasks, select the region where the migration instance is located.

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

    3. Configure the source and destination databases.

      Category

      Parameter

      Description

      N/A

      Task Name

      DTS automatically generates a task name. We recommend that you specify a descriptive name for easy identification. The name does not need to be unique.

      Source Database

      Select DMS Database Instance

      Choose whether to use an existing instance as needed.

      • If you use an existing instance, the database information is automatically filled in. You do not need to enter it again.

      • If you do not use an existing instance, enter the database information below.

      Database Type

      Select PolarDB for MySQL.

      Connection Type

      Select Alibaba Cloud Instance.

      Instance Region

      Select the region where the source PolarDB for MySQL instance resides.

      Cross-account

      This example migrates data within the same Alibaba Cloud account. Select No.

      PolarDB Cluster ID

      Select the ID of the source PolarDB for MySQL cluster.

      Database Account

      Enter the database account of the source PolarDB for MySQL instance. For information about required permissions, see Permissions required for database accounts.

      Database Password

      Enter the password for the database account.

      Encryption

      Select a connection type as needed. For more information about the SSL encryption feature, see Enable SSL encryption.

      Destination Database

      Select DMS Database Instance

      Choose whether to use an existing instance as needed.

      • If you use an existing instance, the database information is automatically filled in. You do not need to enter it again.

      • If you do not use an existing instance, enter the database information below.

      Database Type

      Select DataHub.

      Connection Type

      Select Alibaba Cloud Instance.

      Instance Region

      Select the region where the destination DataHub project resides.

      Project

      Select the ID of the destination DataHub project.

    4. After you complete the configuration, click Test Connectivity and Proceed at the bottom of the page.

      Note

      Ensure that the DTS service IP address segments are 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 DTS server IP addresses to a whitelist.

    5. Configure the task objects.

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

        Parameter

        Description

        Migration Types

        • If you only need to perform a full migration, select both Schema Migration and Full Data Migration.

        • To perform a migration with no downtime, select Schema Migration, Full Data Migration, and Incremental Data Migration.

        Note

        • If you do not select Schema Migration, you must ensure that a database and tables to receive the data exist in the destination database. You can also use the object name mapping feature in the Selected Objects box as needed.

        • If you do not select Incremental Data Migration, do not write new data to the source instance during data migration to ensure data consistency.

        Naming Rules of Additional Columns

        DTS adds columns to destination tables during migration to DataHub. If these column names conflict with existing ones, the migration fails. Select New Rule or Previous Rule based on your business requirements.

        Warning

        Before you select a rule, check whether the additional column names conflict with existing columns in the destination tables. For more information about the rules and definitions of additional columns, see Names and definitions of additional columns.

        Processing Mode for Existing Destination Tables

        • Precheck and Report Errors: Checks whether tables with the same names exist in the destination database. If no tables with the same names exist, the precheck is passed. If tables with the same names exist, an error is reported during the precheck, and the data migration task does not start.

          Note

          If a table in the destination database has the same name but cannot be easily deleted or renamed, you can change the name of the table in the destination database. For more information, see Object name mapping.

        • Ignore Errors and Proceed: Skips the check for tables with the same names.

          Warning

          Selecting Ignore Errors and Proceed may cause data inconsistency and business risks. For example:

          • If the table schemas are consistent and a record in the destination database has the same primary key value as a record in the source database:

            • During full migration, DTS keeps the record in the destination database. The record from the source database is not migrated.

            • During incremental migration, DTS does not keep the record in the destination database. The record from the source database overwrites the record in the destination database.

          • If the table schemas are inconsistent, only some columns of data may be migrated, or the migration may fail. Proceed with caution.

        Case Policy for Destination Object Names

        Configure the case sensitivity policy for database, table, and column names of migration objects in the destination instance. By default, DTS default policy is selected. You can also align with the default policy of the source or destination database. For more information, see Case sensitivity policy for destination object names.

        Source Objects

        Select one or more objects from the Source Objects section. Click the Rightwards arrow icon and add the objects to the Selected Objects section.

        Note

        Select databases or tables as migration objects. If you select tables, other objects such as views, triggers, and stored procedures are not migrated.

        Selected Objects
        Note

        • If you use object name mapping, migration of other objects that depend on the renamed object may fail.

        • To filter data by using WHERE clauses, right-click the table to migrate in the Selected Objects panel and specify the filter conditions in the dialog box that appears. For more information, see Set filter conditions.

        • To select SQL operations for migration at the database or table level, right-click the migration object in the Selected Objects panel and select the desired SQL operations in the dialog box that appears.

        • When migrating at the table level, you can set the Shardkey (partitioning key) by right-clicking the table in the Selected Objects panel and deselecting Sync All Columns in the dialog box that appears.

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

        Parameter

        Description

        Dedicated Cluster for Task Scheduling

        By default, DTS schedules tasks on a shared cluster. You do not need to select one. If you want more stable tasks, you can purchase a dedicated cluster to run DTS migration tasks.

        Retry Time for Failed Connections

        After the migration task starts, if the connection to the source or destination database fails, DTS reports an error and immediately begins to retry the connection. The default retry duration is 720 minutes. You can customize the retry time to a value from 10 to 1440 minutes. We recommend that you set the duration to more than 30 minutes. If DTS reconnects to the source and destination databases within the specified duration, the migration task automatically resumes. Otherwise, the task fails.

        Note

        • For multiple DTS instances that share the same source or destination, the network retry time is determined by the setting of the last created task.

        • Because you are charged for the task during the connection retry period, we recommend that you customize the retry time based on your business needs, or release the DTS instance as soon as possible after the source and destination database instances are released.

        Retry Time for Other Issues

        After the migration task starts, if a non-connectivity issue, such as a DDL or DML execution exception, occurs in the source or destination database, DTS reports an error and immediately begins to retry the operation. The default retry duration is 10 minutes. You can customize the retry time to a value from 1 to 1440 minutes. We recommend that you set the duration to more than 10 minutes. If the related operations succeed within the specified retry duration, the migration task automatically resumes. Otherwise, the task fails.

        Important

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

        Enable Throttling for Full Data Migration

        During full migration, DTS consumes read and write resources on the source and destination databases, which may increase the database load. If required, you can enable throttling for the full migration task. You can set Queries per second (QPS) to the source database, RPS of Full Data Migration, and Data migration speed for full migration (MB/s) to reduce the load on the destination database.

        Note

        • This configuration item is available only if you select Full Data Migration for Migration Types.

        • You can also adjust the full migration speed after the migration instance is running.

        Enable Throttling for Incremental Data Migration

        If required, you can also choose to set speed limits for the incremental migration task. You can set RPS of Incremental Data Migration and Data migration speed for incremental migration (MB/s) to reduce the load on the destination database.

        Note

        • This configuration item is available only if you select Incremental Data Migration for Migration Types.

        • You can also adjust the incremental migration speed after the migration instance is running.

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

        Choose whether DTS writes heartbeat SQL information to the source database while the instance is running.

        • Yes: Does not write heartbeat SQL information to the source database. The DTS instance may display latency.

        • No: Writes heartbeat SQL information to the source database. This may interfere with source database operations like physical backups and cloning.

        Environment Tag

        Select an environment tag to identify the instance. Not required for this example.

        Configure ETL

        Based on your business needs, select whether to configure the ETL feature to process data.

        • Yes: Configures the ETL feature. You must also enter data processing statements in the text box.

        • No: Does not configure the ETL feature.

        Monitoring and Alerting

        Select whether to set alerts and receive alert notifications based on your business needs.

        • No: Does not set an alert.

        • Yes: Configure alerts by setting an alert threshold and an alert notifications. If a migration fails or the latency exceeds the threshold, the system sends an alert notification.

    6. Save the task and run a precheck.

      • To view the parameters for configuring this instance when you call the API operation, move the pointer over the Next: Save Task Settings and Precheck button and click Preview OpenAPI parameters in the bubble that appears.

      • If you do not need to view or have finished viewing the API parameters, click Next: Save Task Settings and Precheck at the bottom of the page.

      Note

      • Before the migration task starts, DTS performs a precheck. The task starts only after it passes the precheck.

      • If the precheck fails, click View Details next to the failed check item, fix the issue based on the prompt, and then run the precheck again.

      • If a warning is reported during the precheck:

        • For check items that cannot be ignored, click View Details next to the failed item, fix the issue based on the prompt, and then run the precheck again.

        • For check items that can be ignored, you can click Confirm Alert Details, Ignore, OK, and Precheck Again to skip the alert item and run the precheck again. If you choose to ignore a warning, it may cause issues such as data inconsistency and pose risks to your business.

    7. Purchase the instance.

      1. When the Success Rate is 100%, click Next: Purchase Instance.

      2. On the Purchase page, select the link specification for the data migration instance. For more information, see the following table.

        Category

        Parameter

        Description

        New Instance Class

        Resource Group Settings

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

        Instance Class

        DTS provides migration specifications with different performance levels. The link specification affects the migration speed. You can select a specification based on your business scenario. For more information, see Data migration link specifications.

      3. After the configuration is complete, read and select Data Transmission Service (Pay-as-you-go) Service Terms.

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

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

        Note

        • If the migration task does not include incremental migration, it stops automatically after the full migration is complete. After the task stops, its Status changes to Completed.

        • If the migration task includes incremental migration, it does not stop automatically. The incremental migration task continues to run. While the incremental migration task is running, the Status of the task is Running.