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    Data Transmission Service:Two-way synchronization between RDS for MySQL and PolarDB for MySQL

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    Data Transmission Service:Two-way synchronization between RDS for MySQL and PolarDB for MySQL

    Last Updated:Jun 03, 2026

    DTS enables two-way data synchronization between an ApsaraDB RDS for MySQL instance and a PolarDB for MySQL cluster.

    Supported source databases

    The following MySQL database types support two-way synchronization with a PolarDB for MySQL cluster. This topic uses an RDS for MySQL instance as an example. The procedure is similar for other source database types.

    • ApsaraDB RDS for MySQL instance

    • 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

    • Self-managed database that is connected over Cloud Enterprise Network (CEN)

    Prerequisites

    Precautions

    Note

    • During schema synchronization, DTS synchronizes foreign keys from the source database to the destination database.

    • During full data synchronization and incremental data synchronization, DTS temporarily disables constraint checks and foreign key cascade operations at the session level. Data inconsistency may occur if cascade update or delete operations are performed on the source database while the task is running.

    Type

    Description

    Source and destination 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:

      MySQL

      • 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.

      PolarDB for MySQL

      • You must enable binary logging and set the loose_polar_log_bin parameter to ON. Otherwise, an error is reported during the precheck and the DTS instance fails to start. For more information about how to enable binary logging and modify parameters, see Enable binary logging and Set cluster and node parameters.

        Note

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

      • The binary logs of the PolarDB for MySQL cluster must be retained for at least 3 days. We recommend that you retain them for 7 days. Otherwise, the DTS task may fail because DTS cannot obtain the binary logs. In extreme cases, this may cause data inconsistency or data loss. Issues caused by a binary log retention period shorter than the required period 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 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.

    Other limits

    • Use the same version for the source and destination databases, or upgrade from a lower version to a higher version to ensure compatibility. Synchronizing from a higher version to a lower version may cause compatibility issues.

    • If your source database uses online DDL operations in temporary table mode—including but not limited to multi-table merge scenarios—or adds function-based indexes to unique key columns, data loss or task failure may occur in the destination database.

    • Resolvers defined by comment syntax do not support synchronous use.

    • If a primary key or unique key conflict occurs while the task is running:

      • 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.

    • While a two-way synchronization task runs, DTS creates a database named dts in the destination databases of both forward and reverse tasks. This prevents circular synchronization. Do not modify this database while the task runs. Ensure the database account used by the task has read and write permissions on this database.

    • If your data includes four-byte characters—such as rare Chinese characters or emojis—the destination database and table must use the utf8mb4 charset.

      Note

      If you use DTS to synchronize table schemas, set the character_set_server parameter at the instance level in the destination database to utf8mb4.

    • Assess the performance of both the source and destination databases before starting synchronization. Run synchronization during off-peak hours. Otherwise, full initialization consumes read and write resources on both databases and may increase database load.

    • Full initialization runs INSERT operations concurrently. This fragments destination tables. After full initialization, the tablespace of the destination instance is larger than that of the source instance.

    • If you synchronize one or more tables—not a full database—do not use tools like pt-online-schema-change to perform online DDL operations on the source tables. Otherwise, synchronization fails.

      You can use Data Management (DMS) to perform online DDL operations. For more information, see Online DDL without locking tables.

    • 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.

    • DTS disables foreign key constraints by default when synchronizing to a destination database. Therefore, cascading operations and deletions in the source database are not synchronized to the destination database.

    • A two-way synchronization task includes forward and reverse synchronization tasks. When you configure or reset the task, if the destination object of one task matches the synchronization object of the other task:

      • Allow only one task to synchronize full and incremental data. The other task supports only incremental synchronization.

      • Data from the source of the current task synchronizes only to the destination of the current task. It does not serve as source data for the other task.

    • You cannot convert datetime data to varchar.

    • If a DDL operation fails in the destination database, the DTS task continues to run. Check the failed DDL in the task logs. For instructions, see View task logs.

    • 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.

    • To synchronize accounts from the source database, meet the prerequisites and review related considerations. For more information, see Migrate database accounts.

    • 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.

    Billing

    Synchronization type

    Pricing

    Schema synchronization and full data synchronization

    Free of charge.

    Incremental data synchronization

    Charged. For more information, see Billing overview.

    Conflict detection

    To ensure data consistency, make sure that data records with the same primary key, business primary key, or unique key are updated in only one of the database instances in the two-way synchronization. If data records are updated on both database instances, DTS the system will apply the conflict resolution policy configured in the task.

    DTS checks and fixes conflicts to maximize the stability of two-way synchronization tasks. DTS can detect the following types of conflicts:

    • Uniqueness conflicts caused by INSERT operations

      In two-way synchronization, if records with the same primary key are inserted into both database instances simultaneously (or in close succession), a uniqueness constraint conflict will be triggered. When the INSERT statement is synchronized to the peer instance, it will fail because a record with the same primary key value already exists.

    • Mismatched records in UPDATE operations

      • If the records to be updated do not exist in the destination instance, DTS converts the UPDATE operation into an INSERT operation. However, uniqueness conflicts may occur.

      • The record to be updated by an UPDATE operation causes a primary key or unique key conflict.

    • Non-existent records to be deleted

      The records to be deleted do not exist in the destination instance. In this case, DTS ignores the DELETE operation regardless of the conflict resolution policy that you specify.

    Important

    • Due to time differences and latency, DTS cannot guarantee 100% conflict prevention. To ensure consistency, update records with the same primary or unique key on only one database instance at a time.

    • DTS provides various conflict resolution strategies for the aforementioned data conflicts, which you can select while configuring two-way data synchronization.

    Supported synchronization topologies

    DTS supports two-way synchronization between an ApsaraDB RDS for MySQL instance and a PolarDB for MySQL cluster.

    Available topologies and usage notes are documented in Synchronization topologies.

    Supported SQL

    Operation type

    SQL statement

    DML

    INSERT, UPDATE, DELETE

    DDL

    • ALTER TABLE, ALTER VIEW

    • CREATE FUNCTION, CREATE INDEX, CREATE PROCEDURE, CREATE TABLE, CREATE VIEW

    • DROP INDEX, DROP TABLE

    • RENAME TABLE

      Important

      The RENAME TABLE operation may cause data inconsistency. For example, if the synchronization object is only a specific table and you rename the table in the source instance during synchronization, the data of the table is not synchronized to the destination database. To prevent this issue, select the entire database to which the table belongs as the synchronization object when you configure the data synchronization task. Make sure that the databases to which the table belongs before and after the RENAME TABLE operation are both included in the synchronization object.

    • TRUNCATE TABLE

    Important

    DDL operations synchronize only in the forward direction (source to destination). Reverse-direction DDL is automatically filtered.

    Database account permissions

    Database

    Permissions

    Actions

    ApsaraDB RDS for MySQL source instance

    Privileged account permissions

    Create an account

    PolarDB for MySQL destination cluster

    Privileged account permissions

    Create and manage a database account

    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 Existing Connection

      • Select the registered database instance with DTS from the drop-down list. The database information below is automatically configured.

        Note

        In the DMS console, this configuration item is Select a DMS database instance.

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

      Database Type

      Select MySQL.

      Access Method

      Select Alibaba Cloud Instance.

      Instance Region

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

      Replicate Data Across Alibaba Cloud Accounts

      For this example, select No, as the database instance belongs to the current 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. Required permissions are listed in Permissions required for database accounts.

      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 Existing Connection

      • Select the registered database instance with DTS from the drop-down list. The database information below is automatically configured.

        Note

        In the DMS console, this configuration item is Select a DMS database instance.

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

      Database Type

      Select PolarDB for MySQL.

      Access Method

      Select Alibaba Cloud Instance.

      Instance Region

      Select the region where the destination PolarDB for MySQL cluster is located.

      Replicate Data Across Alibaba Cloud Accounts

      For this example, select No, as the database instance belongs to the current Alibaba Cloud account.

      PolarDB Cluster ID

      Select the ID of the destination PolarDB for MySQL cluster.

      Database Account

      Enter the database account for the destination PolarDB for MySQL cluster. Required permissions are listed in Permissions required for database accounts.

      Database Password

      Enter the password for the specified database account.

      Encryption

      Select an option based on your business requirements. For more information about SSL encryption, see Configure SSL encryption.

    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 Types

        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.

        Method to Migrate Triggers in Source Database

        Select a trigger synchronization method. Skip if no triggers are involved. Configure the method to synchronize or migrate triggers.

        Note

        This parameter is available only when Synchronization Types is selected for Schema Synchronization.

        Synchronization Topology

        Select Two-way Synchronization.

        Exclude DDL Operations

        • Select Yes to not synchronize DDL operations.

        • Select No to synchronize DDL operations.

          Important

          DDL synchronization is directional. You can enable DDL synchronization only for the forward task (source to destination). The reverse task automatically filters out DDL operations.

        Conflict Resolution Policy

        If any of the preceding conflict types occur, select a conflict resolution policy based on your business requirements.

        • TaskFailed (Fail and report an error upon conflict)

          The task will error out and stop if a conflict occurs. The task enters a failed state and requires manual intervention for recovery.

        • Ignore (Keep the existing record in the destination instance)

          The system skips the conflicting statement and continues the synchronization. The existing record in the destination instance is retained.

        • Overwrite (Overwrite the conflicting record in the destination instance)

          If a conflict occurs, the system overwrites the conflicting record in the destination instance with the data from the source.

        Note

        If the task is paused, restarted, or delayed, these policies do not take effect during the delay. DTS overwrites destination data by default.

        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.

        Whether to migrate Event

        Specify whether to synchronize events from the source database as required. If you select Yes, you must also meet the relevant requirements and perform subsequent operations. For more information, see Synchronize or migrate events.

        Capitalization of Object Names in Destination Instance

        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

        You can select objects at the database, table, or column level. If you select only tables or columns, DTS does not synchronize other object types (such as views, triggers, and stored procedures).

        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 select SQL operations at the database or table level, right-click the object in the Selected Objects box and select operations in the dialog box.

        • To filter data with a WHERE clause, right-click the table in the Selected Objects box and set the filter condition. Set a filter condition.

        • Object name mapping may cause dependent objects to fail to synchronize.

      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?.

        Select the engine type of the destination database

        Select the engine type for the destination database.

        • InnoDB: The default storage engine.

        • X-Engine: A storage engine for online transaction processing (OLTP) databases.

        Copy the temporary table of the Online DDL tool that is generated in the source table to the destination database.

        If the source database uses Data Management (DMS) or gh-ost for online DDL changes, choose whether to synchronize the temporary tables generated during these operations.

        Important

        DTS tasks do not currently support online DDL changes performed by tools like pt-online-schema-change. Using such tools will cause the DTS task to fail.

        • Yes: Synchronizes the temporary tables generated by online DDL changes.

          Note

          If the data of temporary tables generated by online DDL changes is too large, it may cause synchronization latency.

        • No, Adapt to DMS Online DDL: Does not synchronize temporary tables generated by online DDL changes. Instead, it synchronizes only the original DDL statements executed in Data Management (DMS).

          Note

          This approach will cause table locks on the destination database.

        • No, Adapt to gh-ost: Does not the synchronize temporary tables generated by online DDL changes. Instead, it synchronizes only the original DDL statements executed by gh-ost. You can use default or custom regular expressions for gh-ost shadow and trash tables.

          Note

          This approach will cause table locks on the destination database.

        Whether to Migrate Accounts

        Select whether to synchronize account information from the source database. If you select Yes, select accounts and confirm permissions. Authorization methods are described in Migrate database accounts.

        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

        Select an environment tag to identify the instance. Optional 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

        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.

      3. Click Data Verification to configure a data verification task.

        To use the data verification feature, see Configure data verification.

    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.

    8. Configure the reverse synchronization task.

      1. Wait for the initialization of the forward synchronization task to complete and for its Status to change to Running.

      2. Locate the reverse synchronization task and click Configure Task.

      3. Follow Step 3 through Step 6 to configure the reverse synchronization task.

        Important

        • Select the correct source and destination instances for the reverse task. The source is the forward task's destination, and vice versa. Ensure database names, accounts, and passwords are consistent.

        • The Instance Region for source and destination databases cannot be modified in the reverse task. This task requires fewer parameters. Follow the console instructions.

        • When configuring Processing Mode of Conflicting Tables for the reverse task, the check does not apply to tables synchronized by the forward task.

        • The reverse synchronization task automatically filters out DDL operations.

        • The reverse task cannot synchronize objects included in the forward task's Selected Objects.

        • Avoid using object name mapping for the reverse task to prevent data inconsistency.

      4. When the Success Rate reaches 100%, click Back.

    9. After configuring the reverse task, wait until the Status of both tasks is Running. The two-way synchronization setup is complete.