All Products
Search

This Product

    Data Transmission Service:Synchronize self-managed Oracle to PolarDB-X 2.0

    Document Center

    Data Transmission Service:Synchronize self-managed Oracle to PolarDB-X 2.0

    Last Updated:Aug 27, 2026

    This topic describes how to use Data Transmission Service (DTS) to synchronize data from a self-managed Oracle database to a PolarDB-X 2.0 instance.

    Prerequisites

    • You have created a source self-managed Oracle database and a target PolarDB-X 2.0 instance. The source self-managed Oracle database must be version 19c, 18c, 12c, 11g, 10g, or 9i.

    • The self-managed Oracle database runs in ARCHIVELOG mode, and its archived logs have a reasonable retention period and are accessible. For more information, see ARCHIVELOG.

    • Supplemental logging, including supplemental_log_data_pk and supplemental_log_data_ui, is enabled. For more information, see Supplemental Logging.

    • The target PolarDB-X 2.0 instance requires more storage space than the source self-managed Oracle database.

    • Before you synchronize an Oracle source database, understand the capabilities and limitations of Data Transmission Service (DTS) and use Advanced Database & Application Migration (ADAM) to assess your database. This ensures a smooth migration to the cloud. For more information, see Limitations and preparation for Oracle databases and Database assessment overview.

    Limitations

    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.

    Category

    Description

    Limits on the source database

    • Object requirements:

      • Tables must have PRIMARY KEY or UNIQUE constraints with all fields unique. Otherwise, the destination database may contain duplicate data.

      • For Oracle 12c and later, table names cannot exceed 30 bytes.

      • If you select tables as objects and edit them in the destination (such as renaming tables or columns), a single task supports up to 1,000 tables. Exceeding this limit causes a request error. To synchronize more, split tables across multiple tasks or synchronize the entire database.

    • If the source Oracle RAC database connects over Express Connect, specify a VIP when you configure the task.

    • For self-managed Oracle RAC databases, use a VIP instead of a SCAN IP address. Node failover is not supported after you specify the VIP.

    • The redo logging and archive logging features must be enabled.

      Note

      For incremental-only synchronization, retain redo logs and archive logs for more than 24 hours. For full + incremental synchronization, retain them for at least seven days. After full synchronization completes, you can set retention to more than 24 hours. Insufficient retention may cause task failures, data inconsistency, or loss, and the DTS SLA may not apply.

    • A primary/secondary switchover on the source database during synchronization causes the task to fail.

    • If the data contains a VARCHAR2 empty string (treated as null by Oracle) and the destination column has a NOT NULL constraint, the task fails.

    • If a table has the Fine-Grained Audit (FGA) policy enabled, DTS cannot detect the ORA_ROWSCN pseudocolumn, which causes the task to fail.

      Note

      Disable the FGA policy for the table, or exclude the table from synchronization.

    • Do not update LONGTEXT fields during synchronization. Otherwise, the task fails.

    • 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.

    Other limits

    • Do not use Oracle Data Pump to write data to the source database during incremental synchronization. Otherwise, data loss may occur.

    • Synchronize data during off-peak hours. During initial full synchronization, DTS consumes read and write resources on both databases, which may increase server load.

    • External tables cannot be synchronized.

    • DTS calculates synchronization latency from the timestamp of the latest synchronized data and the current source timestamp. If no DML operations run on the source for a long time, the latency may be inaccurate. Perform a DML operation on the source to refresh the latency.

      Note

      If you synchronize an entire database, create a heartbeat table that updates every second.

    • During synchronization, use only DTS to write to the destination database. Writing with other tools (for example, DMS online DDL) may cause data loss or inconsistency.

    • 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.

    • If the destination PolarDB-X 2.0 table has auto partitioning enabled (auto_partition=true), each DDL statement executed on the source can contain only one alter_specification. Otherwise, DTS reports an error (TDDL-4998: Multi alter specifications when create GSI not support yet). To execute a DDL statement that contains multiple alter_specification items, split each alter_specification into a separate DDL statement and execute them one by one. For more information, see ALTER TABLE (DRDS mode) and ALTER TABLE (AUTO mode).

    Billing

    Synchronization type

    Pricing

    Schema synchronization and full data synchronization

    Free of charge.

    Incremental data synchronization

    Charged. For more information, see Billing overview.

    Synchronization topologies

    • One-way, one-to-one synchronization.

    • One-way, one-to-many synchronization.

    • One-way, many-to-one synchronization.

    • One-way cascade synchronization.

    For details about these synchronization topologies, see Synchronization topology.

    Supported SQL operations

    Operation type

    SQL statement

    DML

    INSERT, UPDATE, and DELETE

    DDL

    • CREATE TABLE, ALTER TABLE, DROP TABLE, RENAME TABLE, and TRUNCATE TABLE

      Important

      The RENAME TABLE operation may cause data inconsistency. For example, if the synchronization object is a single table and you rename it on the source instance during synchronization, the data of that table is not synchronized to the destination database. To avoid this issue, you can configure the task to synchronize the entire database that contains the table. Make sure that the database to which the table belongs both before and after the RENAME TABLE operation is included in the synchronization objects.

    • CREATE VIEW, ALTER VIEW, and DROP VIEW

    • CREATE PROCEDURE, ALTER PROCEDURE, and DROP PROCEDURE

    • CREATE FUNCTION, DROP FUNCTION, CREATE TRIGGER, and DROP TRIGGER

    • CREATE INDEX and DROP INDEX

    Required permissions

    Database

    Required permissions

    Procedure

    Self-managed Oracle database

    Requires fine-grained permissions.

    Prepare a database account, CREATE USER, and GRANT.
    Important

    You must also enable archive logs and supplemental logging to capture incremental data changes. For more information, see Database configuration.

    Procedure

    1. Go to the Data Synchronization Tasks page.

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

      2. In the top navigation bar, click Data + AI.

      3. In the left-side navigation pane, choose DTS (DTS) > Data Synchronization.

      Note

    2. Click Create Task to open 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 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 Oracle.

      Connection Type

      Select the connection type that matches the deployment location of the source database. This topic uses Self-managed Database on ECS as an example.

      Note

      If the source instance is a self-managed database, you must also perform the required preparations.

      Instance Region

      Select the region of the self-managed Oracle database.

      ECS Instance ID

      Select the ECS instance ID of the self-managed Oracle database.

      Port

      Enter the service port of the self-managed Oracle database. The default value is 1521.

      Oracle Type

      In this example, select RAC or PDB Instance.

      • Non-RAC Instance: If you select this option, you must also specify the SID.

      • RAC or PDB Instance: If you select this option, you must also specify the Service Name.

      Database Account

      Enter the database account of the source self-managed Oracle instance.

      Database Password

      Enter the password for the specified database account.

      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-X 2.0.

      Connection Type

      Select Alibaba Cloud Instance.

      Instance Region

      Select the region of the destination PolarDB-X 2.0 instance.

      Instance ID

      Select the ID of the destination PolarDB-X 2.0 instance.

      Database Account

      Enter the database account of the destination PolarDB-X 2.0 instance. This account requires read and write permissions.

      Database Password

      Enter the password for the specified database account.

    4. After the configuration is complete, click Test Connectivity and Proceed at the bottom of the page. In the CIDR Blocks of DTS Servers dialog box, click Test Connectivity.

      Note

      Ensure that the IP address blocks of the DTS service are added to the security settings of the source and destination databases, either automatically or manually, to allow access from DTS servers. For more information, see Add the IP address whitelist of DTS servers.

    5. Configure the task objects.

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

        Parameter

        Description

        Synchronization Type

        The synchronization types. By default, Incremental Data Synchronization is selected. You must also select Schema Synchronization and Full Data Synchronization. After the precheck is complete, DTS synchronizes the historical data of the selected objects from the source database to the destination cluster. The historical data is the basis for subsequent incremental synchronization.

        Processing Mode for Existing Destination 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.

        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 the SQL operations to synchronize at the database or table level, right-click an object in the Selected Objects box and select the desired SQL operations in the dialog box that appears.

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

      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?.

        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. In this example, no tag is needed.

        Actual Write Code

        You can select the encoding type for data written to the destination based on your business requirements.

        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.