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    Data Transmission Service:Migrate RDS for MySQL to PolarDB-X 1.0

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    Data Transmission Service:Migrate RDS for MySQL to PolarDB-X 1.0

    Last Updated:Jul 01, 2026

    You can use Data Transmission Service (DTS) to migrate data from an ApsaraDB RDS for MySQL instance to a PolarDB-X 1.0 instance.

    Supported source databases

    You can migrate data from the following types of MySQL source databases to a PolarDB-X 1.0 instance. This topic uses an ApsaraDB RDS for MySQL instance to demonstrate the configuration procedure. The procedure for other source database types is similar.

    • An ApsaraDB RDS for MySQL instance.

    • The following types of self-managed databases:

      • Self-managed database with a public IP address
      • Self-managed database that is hosted on Elastic Compute Service (ECS)
      • Self-managed database that is connected over Express Connect, VPN Gateway, or Smart Access Gateway
      • Self-managed database that is connected over Database Gateway

    Prerequisites

    • You must have a source ApsaraDB RDS for MySQL instance. For more information, see Create an ApsaraDB RDS for MySQL instance.

      Note

      For an incremental migration, ensure that the character set of the source data is not utf8mb3.

    • You must have a PolarDB-X 1.0 instance. For more information, see Create a PolarDB-X 1.0 instance.

    • The PolarDB-X 1.0 instance must have more storage space than is used by the source ApsaraDB RDS for MySQL instance.

    Limitations

    Type

    Description

    Source database limitations

    • Bandwidth requirement: The server that hosts the source database must have sufficient outbound bandwidth. Otherwise, this affects the data migration speed.

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

    • If you migrate data at the table level and need to perform edits (such as table column mapping), a single data migration task can support a maximum of 1,000 tables. If this limit is exceeded, an error is reported after you submit the task. In this case, we recommend splitting the tables into multiple batches with separate tasks, or migrating the entire database in a single task.

    • If you need incremental migration, enable binary logging:

      • Set binlog_format to ROW and binlog_row_image to FULL. Otherwise, the precheck fails and the task cannot start.

        Important

        If your self-managed MySQL source is a dual-master cluster—where each instance acts as both master and slave—enable the log_slave_updates parameter. This ensures DTS can read all binary logs.

      • For RDS for MySQL instances, retain local binary logs for at least three days (seven days recommended). For self-managed MySQL databases, retain local binary logs for at least seven days. If DTS cannot access binary logs, the task fails. In extreme cases, data inconsistency or data loss may occur. Issues caused by binary log retention periods shorter than DTS requires are not covered under the DTS SLA.

        Note

        To set the retention period for local binary logs on an RDS for MySQL instance, see Automatically delete local logs.

    • During the schema migration and full migration phases, do not perform DDL operations that change the database or table structure. Otherwise, the data migration task will fail.

      Note

      During the full migration phase, DTS queries the source database. This creates a metadata lock that may block DDL operations on the source database.

    • If you perform only a full data migration, do not write new data to the source database. Otherwise, the data in the source and destination databases will become inconsistent. To maintain data consistency in real time, select both full data migration and incremental data migration.

    • If you need incremental migration, RDS for MySQL instances that do not record transaction logs—such as RDS for MySQL 5.6 read-only instances—are not supported as sources.

    • The storage type of a PolarDB-X 1.0 instance must be ApsaraDB RDS for MySQL, which refers to custom ApsaraDB RDS instances. PolarDB for MySQL is not supported.

    • DTS does not migrate data generated by changes that do not write to binary logs. Examples include data restored from physical backups or created by cascade operations.

      Note

      If this occurs, re-run full migration after your business allows it.

    • If your source MySQL database is version 8.0.23 or later and contains invisible hidden columns, DTS cannot read those columns. This may cause data loss.

      Note

      Run ALTER TABLE <table_name> ALTER COLUMN <column_name> SET VISIBLE; to make the hidden column visible. For more information, see Invisible Columns.

    Other limitations

    • Incremental data migration does not support data that uses the utf8mb3 character set. Otherwise, the task will fail.

    • If your source database uses temporary-table-mode online DDL operations—including multi-table merge scenarios—or adds function-based indexes to unique key columns, data loss or task failure may occur on the destination database.

    • Schema migration is not supported. Before you configure a migration task, you must create the corresponding databases and tables in the destination PolarDB-X 1.0 instance.

    • Before you migrate data, evaluate the performance of the source and destination databases. We recommend performing data migration during off-peak hours. During full data migration, DTS consumes some read and write resources on both the source and destination databases, which may increase the database load.

    • Full data migration runs concurrent INSERT operations, which can cause table fragmentation in the destination database. As a result, after the full data migration is complete, the table storage space in the destination database is larger than in the source instance.

    • Confirm that the migration precision for columns of the FLOAT or DOUBLE data type meets your business requirements. DTS reads values from these columns using the ROUND(COLUMN,PRECISION) function. If you do not explicitly define the precision, DTS uses a precision of 38 digits for FLOAT and 308 digits for DOUBLE.

    • DTS attempts to resume failed migration tasks within seven days. Before you switch your workloads to the destination instance, you must stop or release the task. Alternatively, use the revoke command to revoke write permissions from the account that DTS uses to access the destination instance. This prevents an automatically resumed task from overwriting data in the destination instance.

    • If your RDS for MySQL instance has Always-Encrypted enabled, full migration is not supported.

      Note

      RDS for MySQL instances with Transparent Data Encryption (TDE) enabled support schema migration, full migration, and incremental migration.

    • 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.

    Special cases

    • For self-managed MySQL sources:

      • A master–standby switchover on the source database causes the migration task to fail.

      • DTS calculates latency by comparing the timestamp of the last record migrated to the destination database with the current time. If no DML operations run on the source for a long time, latency reporting becomes inaccurate. If latency appears too high, run a DML operation on the source to update the latency value.

        Note

        If you select full-database migration, create a heartbeat table. Update or write to it every second.

      • DTS periodically runs CREATE DATABASE IF NOT EXISTS `test` on the source database to advance the binary log offset.

      • If your source is Amazon Aurora MySQL or another clustered MySQL instance, ensure the domain name or IP address configured for the task—and its DNS resolution—always points to a read–write (RW) node. Otherwise, the migration task may fail.

    • For RDS for MySQL sources:

      • If you need incremental migration, RDS for MySQL instances that do not record transaction logs—such as RDS for MySQL 5.6 read-only instances—are not supported as sources.

      • DTS periodically runs CREATE DATABASE IF NOT EXISTS `test` on the source database to advance the binary log offset.

    Billing

    Migration type

    Instance configuration fee

    Internet traffic fee

    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

    • Full migration

      DTS migrates all historical data of the specified 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, and DELETE

    Database account permissions

    Database

    Full data migration

    Incremental data migration

    ApsaraDB RDS for MySQL instance

    SELECT permission

    REPLICATION CLIENT, REPLICATION SLAVE, SHOW VIEW, and SELECT permissions

    PolarDB-X 1.0 instance

    Read and write permissions

    For more information about creating database accounts and granting permissions, see the following topics:

    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.

      Warning

      After selecting the source and destination instances, read the Limits at the top of the page to ensure your data migration task can be created and run successfully.

      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 Existing Connection

      • To use a database instance that has been added to the system (created or saved), select the desired database instance from the drop-down list. The database information below will be automatically configured.

        Note

        In the DMS console, this parameter is named Select a DMS database instance..

      • If you have not registered the database instance with the system, or do not need to use a registered instance, manually configure the database information below.

      Database Type

      Select MySQL.

      Connection Type

      Select Alibaba Cloud Instance.

      Instance Region

      Select the region where the source RDS for MySQL instance is located.

      Cross-account

      In this example, data is migrated within the same Alibaba Cloud account. Select No.

      RDS Instance ID

      Select the ID of the source RDS for MySQL instance.

      Database Account

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

      Database Password

      Enter the password of the database account.

      Connection Method

      Select Non-encrypted or SSL-encrypted based on your database requirements. If you set this parameter to SSL-encrypted, you must enable SSL encryption for the RDS for MySQL instance beforehand. For more information, see Quickly enable SSL encryption using a cloud certificate.

      Destination Database

      Select Existing Connection

      • To use a database instance that has been added to the system (created or saved), select the desired database instance from the drop-down list. The database information below will be automatically configured.

        Note

        In the DMS console, this parameter is named Select a DMS database instance..

      • If you have not registered the database instance with the system, or do not need to use a registered instance, manually configure the database information below.

      Database Type

      Select PolarDB-X 1.0.

      Connection Type

      Select Alibaba Cloud Instance.

      Instance Region

      Select the region where the destination PolarDB-X 1.0 instance is located.

      Instance ID

      Select the destination PolarDB-X 1.0 instance.

      Database Account

      Enter the database account of the destination PolarDB-X 1.0 instance. For information about the required permissions, see Permissions required for database accounts.

      Database Password

      Enter the password of the database account.

    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 Full Data Migration.

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

        Note

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

        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.

        Capitalization of Object Names in Destination Instance

        You can configure the case sensitivity policy for the names of migrated objects, such as databases, tables, and columns, in the destination instance. By default, DTS default policy is selected. You can also choose to keep the case sensitivity consistent with the default policy of the source or destination database. For more information, see Case sensitivity of object names in the destination database.

        Source Objects

        In the Source Objects box, click the objects to migrate, and then click Right arrow to move them to the Selected Objects box.

        Note

        Migration objects are selected at the table level.

        Selected Objects
        Note

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

        • To specify a WHERE clause to filter data, right-click the table to be migrated in the Selected Objects box, and then specify the filter condition in the dialog box that appears. For more information, see Set filter conditions.

        • To select the DML operations for incremental data migration, right-click the object to be migrated in the Selected Objects box, and then select the desired DML operations 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.

        Environment Tag

        You can select an environment tag to identify the instance. This is not required for this example.

        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.

        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.