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    Data Transmission Service:Synchronize RDS for MySQL to DataHub

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    Data Transmission Service:Synchronize RDS for MySQL to DataHub

    Last Updated:Jul 16, 2026

    DataHub is a streaming data processing platform that lets you publish, subscribe to, and distribute streaming data, making it easy to build analytics and applications. Use DTS to synchronize data from ApsaraDB RDS for MySQL to DataHub to quickly enable real-time analysis using big data services such as stream computing.

    Prerequisites

    Usage notes

    Note

    DTS does not synchronize foreign keys from the source database to the destination database. Therefore, cascading operations on the source database are not synchronized to the destination database.

    Type

    Description

    Source database limits

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

    • If you synchronize at the table level and need to edit mappings (such as column name mapping), each synchronization task supports up to 1,000 tables. If you exceed this limit, the task fails with an error. To fix this, split the tables across multiple tasks or configure a full-database synchronization task.

    • Binary logs:

      • ApsaraDB RDS for MySQL enables binary logging by default. Ensure that the binlog_row_image parameter is set to full. Otherwise, the precheck fails and the synchronization task cannot start. For instructions, see Configure instance parameters.

        Important

        • If your source instance is a self-managed MySQL database, enable binary logging and set binlog_format to row and binlog_row_image to full.

        • If your self-managed MySQL database is a dual-primary cluster (where both nodes act as primary and secondary), enable the log_slave_updates parameter so DTS can capture all binary log events. For instructions, see Create an account and configure binary logging for a self-managed MySQL database.

      • The local binary logs for an ApsaraDB RDS for MySQL instance must be retained for at least three days (seven days is recommended). For a self-managed MySQL database, retain local binary logs for at least seven days. Otherwise, DTS may fail to retrieve binary logs, causing the task to fail. In extreme cases, this may cause data inconsistency or data loss. Issues caused by binary log retention periods shorter than DTS requires are not covered under the DTS SLA.

        Note

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

    • Do not run DDL operations that change database or table schemas during schema synchronization or full synchronization. Otherwise, the synchronization task fails.

      Note

      During full synchronization, DTS queries the source database. This creates metadata locks that may block DDL operations on the source database.

    • Data generated by changes that do not write to binary logs—such as data restored from physical backups or created by cascade operations—is not synchronized to the destination database.

      Note

      If this occurs, remove the affected database or table from the synchronization objects. Then add it back. You can do this only if your business allows it. For more information, see Modify synchronization objects.

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

      Note

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

    • MySQL compatibility: When DTS synchronizes data from a MySQL-family source database, it relies on the standard MySQL protocol and Binlog format, and behaviors incompatible with standard MySQL are not supported. If your source database claims MySQL compatibility but behaves differently from MySQL (for example, when OceanBase is connected as a source in MySQL mode, the timestamp of the trailing rotate event in the Binlog is 0, which differs from MySQL), the DTS synchronization task may fail.

    Other limits

    • A single String field in DataHub supports up to 2 MB.

    • DTS does not support synchronizing indexes, partitions, views, stored procedures, functions, triggers, or foreign keys.

    • If your source table contains a record_id column, use field mapping to rename it in the destination instance. Otherwise, the task fails. For instructions, see Database and table column name mapping.

    • Do not write data to the destination database except through DTS while synchronization is running. Otherwise, data inconsistency may occur between the source and destination databases. For example, if you use DMS to perform online DDL operations while other data is written to the destination database, data loss may occur.

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

      Note

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

    • 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 a self-managed MySQL source database:

      • If a primary/secondary switchover occurs in the source database during synchronization, the task fails.

      • DTS calculates latency by comparing the timestamp of the last synchronized record with the current time. If no DML operations run for a long time in the source database, latency reporting may become inaccurate. If latency appears too high, run a DML operation in the source database to update the latency.

        Note

        If you select a full database for synchronization, create a heartbeat table. Update or write to this table every second.

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

      • If your source database is Amazon Aurora MySQL or another clustered MySQL instance, ensure the domain name or IP address used in the task configuration—and its DNS resolution—always points to a read/write (RW) node. Otherwise, synchronization may fail.

    • For an ApsaraDB RDS for MySQL source database:

      • Read-only instances—such as ApsaraDB RDS for MySQL 5.6 read-only instances—that do not record transaction logs cannot serve as source databases.

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

    Supported synchronization topologies

    • One-way one-to-one synchronization.

    • One-way one-to-many synchronization.

    • One-way many-to-one synchronization.

    To learn about each synchronization topology and its considerations, see Synchronization topologies.

    Supported SQL operations

    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.

    Procedure

    1. Go to the data synchronization task list page in the destination region. You can do this in one of two ways.

      DTS console

      1. Log on to the DTS console.

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

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

      DMS console

      Note

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

      1. Log on to the DMS console.

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

      3. To the right of Data Synchronization Tasks, select the region of the synchronization instance.

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

    3. Configure the source and destination databases.

      Warning

      After you select the source and destination instances, review the Limits at the top of the page. Otherwise, the task may fail or data inconsistency may occur.

      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 MySQL.

      Connection Type

      Select Alibaba Cloud Instance.

      Instance Region

      Select the region where the source ApsaraDB RDS for MySQL instance resides.

      Cross-account

      Select No. This tutorial is for data synchronization within the same Alibaba Cloud account.

      RDS Instance ID

      Select the ID of the source ApsaraDB RDS for MySQL instance.

      Database Account

      Enter the database account for the source ApsaraDB RDS for MySQL instance. The account must have read permissions on the synchronization objects.

      Database Password

      Enter the password for the specified database account.

      Encryption

      Select Non-encrypted or SSL-encrypted as needed. If you set this to SSL-encrypted, you must enable SSL encryption for the RDS for MySQL instance beforehand. For more information, see Use a cloud certificate to quickly enable SSL link 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 instance resides.

      Project

      Select the destination DataHub Project.

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

      Note

      • Ensure that you add the CIDR blocks of the DTS servers (either automatically or manually) to the security settings of both the source and destination databases to allow access. For more information, see Add the IP address whitelist of DTS servers.

      • If the source or destination is a self-managed database (i.e., the Access Method is not Alibaba Cloud Instance), you must also click Test Connectivity in the CIDR Blocks of DTS Servers dialog box.

    5. Configure the task objects.

      1. On the Configure Objects page, specify the objects to synchronize.

        Parameter

        Description

        Synchronization Type

        DTS always selects Incremental Data Synchronization. By default, you must also select Schema Synchronization and Full Data Synchronization. After the precheck, DTS initializes the destination cluster with the full data of the selected source objects, which serves as the baseline for subsequent incremental synchronization.

        Naming Rules of Additional Columns

        When DTS synchronizes data to DataHub, it adds additional columns to the destination table. If a name conflict occurs between an additional column and an existing column in the destination table, the synchronization task fails. Select New Rule or Previous Rule based on your business needs.

        Warning

        Before you select a rule, evaluate whether the additional columns conflict with existing columns in the destination table. Name conflicts can cause data loss or task failures. For more information about the rules and definitions of the additional columns, see Additional column names and definitions.

        Processing Mode of Conflicting Tables

        • Precheck and Report Errors: Checks for tables with the same names in the destination database. If any tables with the same names are found, an error is reported during the precheck and the data synchronization task does not start. Otherwise, the precheck is successful.

          Note

          If you cannot delete or rename the table with the same name in the destination database, you can map it to a different name in the destination. For more information, see Object name mapping.

        • Ignore Errors and Proceed: Skips the check for tables with the same name in the destination database.

          Warning

          Selecting Ignore Errors and Proceed may cause data inconsistency and put your business at risk. For example:

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

            • During full data synchronization, DTS retains the destination record and skips the source record.

            • During incremental synchronization, DTS overwrites the destination record with the source record.

          • If the table schemas are inconsistent, data initialization may fail. This can result in only partial data synchronization or a complete synchronization failure. Use with caution.

        Case Policy for Destination Object Names

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

        Source Objects

        In the Source Objects box, click the objects, and then click 向右 to move them to the Selected Objects box.

        Note

        Synchronization objects are selected at the table level.

        Selected Objects

        • To rename a single object in the destination instance, right-click the object in the Selected Objects box. For more information, see Map a single object name.

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

        Note

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

        • Right-click the table in the Selected Objects box, clear the Sync All Columns checkbox in the dialog box that appears, and then set the shard key. The shard key is used for data partitioning.

      2. Click Next: Advanced Settings.

        Parameter

        Description

        Dedicated Cluster for Task Scheduling

        By default, DTS uses a shared cluster for tasks, so you do not need to make a selection. For greater task stability, you can purchase a dedicated cluster to run the DTS synchronization task. For more information, see What is a DTS dedicated cluster?.

        Set Alerts

        Choose whether to set up alerts. If the synchronization fails or the latency exceeds the specified threshold, DTS sends a notification to the alert contacts.

        Retry Time for Failed Connections

        If the connection to the source or destination database fails after the synchronization task starts, 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 1,440 minutes. We recommend a duration of 30 minutes or more. If the connection is restored within this period, the task resumes automatically. Otherwise, the task fails.

        Note

        • If multiple DTS instances (e.g., Instance A and B) share a source or destination, DTS uses the shortest configured retry duration (e.g., 30 minutes for A, 60 for B, so 30 minutes is used) for all instances.

        • DTS charges for task runtime during connection retries. Set a custom duration based on your business needs, or release the DTS instance promptly after you release the source/destination instances.

        Retry Time for Other Issues

        If a non-connection issue (e.g., a DDL or DML execution error) occurs, DTS reports an error and immediately retries the operation. The default retry duration is 10 minutes. You can also customize the retry time to a value from 1 to 1,440 minutes. We recommend a duration of 10 minutes or more. If the related operations succeed within the set retry time, the synchronization task automatically resumes. Otherwise, the task fails.

        Important

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

        Enable Throttling for Full Data Synchronization

        During full data synchronization, DTS consumes read and write resources from the source and destination databases, which can increase their load. To mitigate pressure on the destination database, you can limit the migration rate by setting Queries per second (QPS) to the source database, RPS of Full Data Migration, and Data migration speed for full migration (MB/s).

        Note

        Enable Throttling for Incremental Data Synchronization

        You can also limit the incremental synchronization rate to reduce pressure on the destination database by setting RPS of Incremental Data Synchronization and Data synchronization speed for incremental synchronization (MB/s).

        Environment Tag

        You can select an environment tag to identify the instance based on your business requirements. For this example, you do not need to select a tag.

        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

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

        Monitoring and Alerting

        Choose whether to set up alerts. If the synchronization fails or the latency exceeds the specified threshold, DTS sends a notification to the alert contacts.

    6. Save the task and perform a precheck.

      • To view the parameters for configuring this instance via an API operation, hover over the Next: Save Task Settings and Precheck button and click Preview OpenAPI parameters in the tooltip.

      • If you have finished viewing the API parameters, click Next: Save Task Settings and Precheck at the bottom of the page.

      Note

      • Before a synchronization task starts, DTS performs a precheck. You can start the task only if the precheck passes.

      • If the precheck fails, click View Details next to the failed item, fix the issue as prompted, and then rerun the precheck.

      • If the precheck generates warnings:

        • For non-ignorable warning, click View Details next to the item, fix the issue as prompted, and run the precheck again.

        • For ignorable warnings, you can bypass them by clicking Confirm Alert Details, then Ignore, and then OK. Finally, click Precheck Again to skip the warning and run the precheck again. Ignoring precheck warnings may lead to data inconsistencies and other business risks. Proceed with caution.

    7. Purchase the instance.

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

      2. On the Purchase page, select the billing method and link specifications for the data synchronization instance. For more information, see the following table.

        Category

        Parameter

        Description

        New Instance Class

        Billing Method

        • Subscription: You pay upfront for a specific duration. This is cost-effective for long-term, continuous tasks.

        • Pay-as-you-go: You are billed hourly for actual usage. This is ideal for short-term or test tasks, as you can release the instance at any time to save costs.

        Resource Group Settings

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

        Instance Class

        DTS offers synchronization specifications at different performance levels that affect the synchronization rate. Select a specification based on your business requirements. For more information, see Data synchronization link specifications.

        Subscription Duration

        In subscription mode, select the duration and quantity of the instance. Monthly options range from 1 to 9 months. Yearly options include 1, 2, 3, or 5 years.

        Note

        This option appears only when the billing method is Subscription.

      3. Read and select the checkbox for Data Transmission Service (Pay-as-you-go) Service Terms.

      4. Click Buy and Start, and then click OK in the OK dialog box.

        You can monitor the task progress on the data synchronization page.

    Topic schema

    When DTS synchronizes data changes to a topic in a DataHub instance, it adds several additional columns to the topic's schema. These columns store metadata about the data changes, as the following example shows.

    Note

    In this example, the data fields are id, name, and address. Because you selected the legacy additional column rules when you configured data synchronization, DTS adds the dts_ prefix to these data fields.

    Topic定义

    The following table describes the additional columns.

    Legacy name

    New name

    Type

    Description

    dts_record_id

    new_dts_sync_dts_record_id

    String

    The unique ID of the incremental log record.

    Note

    • Normally, the ID is globally unique and auto-incrementing. In disaster recovery scenarios, however, rollbacks can occur, so these properties are not guaranteed.

    • For an UPDATE operation, DTS splits the update into two records: one with the pre-update values and another with the post-update values. Both records share the same dts_record_id value.

    dts_operation_flag

    new_dts_sync_dts_operation_flag

    String

    The operation type. Valid values:

    • I: INSERT operation.

    • D: DELETE operation.

    • U: UPDATE operation.

    • F: full data synchronization.

    dts_instance_id

    new_dts_sync_dts_instance_id

    String

    The server ID of the database.

    dts_db_name

    new_dts_sync_dts_db_name

    String

    The database name.

    dts_table_name

    new_dts_sync_dts_table_name

    String

    The table name.

    dts_utc_timestamp

    new_dts_sync_dts_utc_timestamp

    String

    The UTC timestamp of the operation, sourced from the binlog.

    dts_before_flag

    new_dts_sync_dts_before_flag

    String

    Indicates whether the record contains the pre-update values. Valid values: Y and N.

    dts_after_flag

    new_dts_sync_dts_after_flag

    String

    Indicates whether the record contains the post-update values. Valid values: Y and N.

    dts_before_flag and dts_after_flag

    The values of the dts_before_flag and dts_after_flag fields in an incremental log depend on the operation type:

    • INSERT

      For an INSERT operation, all column values represent the newly inserted data, which is the post-update value. Therefore, dts_before_flag is N and dts_after_flag is Y.

      INSERT操作

    • UPDATE

      For an UPDATE operation, DTS splits the operation into two incremental log entries. These two entries share the same values for dts_record_id, dts_operation_flag, and dts_utc_timestamp.

      The first log entry records the pre-update value, where dts_before_flag is Y and dts_after_flag is N. The second entry records the post-update value, where dts_before_flag is N and dts_after_flag is Y.

      UPDATE操作

    • DELETE

      For a DELETE operation, all column values in the incremental log represent the deleted data, which is the pre-update value. Therefore, dts_before_flag is Y and dts_after_flag is N.

      DELETE操作