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    Data Transmission Service:Data migration between ApsaraDB RDS for PostgreSQL instances

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    Data Transmission Service:Data migration between ApsaraDB RDS for PostgreSQL instances

    Last Updated:Jul 10, 2026

    This topic describes how to use Data Transmission Service (DTS) for schema migration, full data migration, and incremental data migration between ApsaraDB RDS for PostgreSQL instances. By combining these three migration types, you can migrate your database without downtime.

    Prerequisites

    • You have created the source and destination ApsaraDB RDS for PostgreSQL instances. For more information, see Create an ApsaraDB RDS for PostgreSQL instance.

      Note

      • For information about the supported versions of the source and destination databases, see Overview of migration scenarios.

      • To ensure compatibility, the destination database should run the same or a later version than the source database. Migrating data to an earlier version may cause compatibility issues.

    • The destination ApsaraDB RDS for PostgreSQL instance must have more storage space than the source ApsaraDB RDS for PostgreSQL instance uses.

    Usage notes

    Type

    Description

    Source database limits

    • Tables selected for migration must have a primary key or a unique constraint, and the fields in the constraint must be unique. Otherwise, duplicate data may occur in the destination database.

      Note

      If the destination table was not created by Data Transmission Service (DTS) because you did not select Schema Migration as the Migration Types, you must ensure that the destination table has the same primary key or non-null unique constraint as the source table. Otherwise, duplicate data may occur in the destination database.

      The name of the database to be migrated cannot contain hyphens (-), for example, dts-testdata.

    • If you select tables as the migration objects and need to edit them (for example, by mapping table or column names), a single migration task can migrate up to 1,000 tables. Exceeding this limit causes an error upon task submission. In this case, split the tables across multiple tasks or configure a task to migrate the entire database.

    • DTS does not migrate temporary tables, internal triggers, or certain functions (such as C-language and internal functions for PROCEDURE and FUNCTION) from the source database. DTS supports migrating some custom data types (COMPOSITE, ENUM, or RANGE) and the following constraints: primary key, foreign key, unique, and CHECK.

    • For an incremental data migration, the following write-ahead logging (WAL) requirements apply:

      • The wal_level parameter must be set to logical.

      • For an incremental data migration task, the WAL in the source database must be retained for more than 24 hours. For a task that includes both full and incremental data migration, DTS requires that the WAL be retained for at least 7 days. After the full data migration is complete, you can reduce the retention period to more than 24 hours. If DTS cannot obtain the required WAL, the migration task may fail. In extreme cases, data inconsistency or loss may occur. Issues caused by a WAL retention period shorter than the required duration are not covered by the DTS Service Level Agreement (SLA).

    • Limits on operations in the source database:

      • During the schema migration and full data migration phases, do not perform DDL operations, as they will cause the migration task to fail.

      • If you perform only a full data migration, do not write new data to the source database. Doing so causes data inconsistency between the source and destination databases. To ensure real-time data consistency, select a migration type that includes schema migration, full data migration, and incremental data migration.

      • Due to the limitations of logical subscriptions, if a migration instance that includes incremental data migration is running and the size of a single row to be migrated exceeds 256 MB after an incremental change, the migration instance fails irrecoverably, and you must reconfigure it.

    • If the source database has long-running transactions and the instance is configured for an incremental migration task, the write-ahead logging (WAL) generated before the transactions are committed cannot be cleared. This may cause WAL to accumulate and exhaust the disk space of the source database.

    • If you perform a major version upgrade on the source database while a migration instance is running, the instance fails irrecoverably, and you must reconfigure it.

    • Tables with generated columns in PostgreSQL 18 do not support migration. If you configure migration for such tables, DML operations on those tables will be blocked.

    Other limits

    • To prevent logical subscription interruptions caused by a failover and ensure a stable data migration task, you must enable Logical Replication Slot Failover for your ApsaraDB RDS for PostgreSQL instance. For instructions, see Logical Replication Slot Failover.

    • DTS migrates only one database per task. To migrate multiple databases, configure a separate task for each one.

    • DTS does not support migrating TimescaleDB extension tables, tables with cross-schema inheritance, or tables with expression-based unique indexes.

    • Schemas created by plug-ins cannot be migrated and are not available for selection in the console during task configuration.

    • If a table to be migrated contains a column of the SERIAL type, a sequence is automatically created for that column in the source database. Therefore, when you configure Source Objects, if the Migration Types includes Schema Migration, we recommend that you also select Sequence or migrate the entire schema. Otherwise, the migration instance may fail.

    • For tasks that include incremental data migration, you must run the ALTER TABLE schema.table REPLICA IDENTITY FULL; command on the tables to be migrated in the source database before you write data to them. This ensures data consistency for the tables in the following two scenarios. To prevent deadlocks, avoid table-locking operations while this command runs. If you skip the related checks during the precheck, DTS automatically runs this command when it initializes the instance.

      • When the instance runs for the first time.

      • When the migration object granularity is set to Schema and a new table is created in the schema or an existing table is rebuilt by using the RENAME command.

      Note

      • In the command, replace schema and table with the schema name and table name of the data to be migrated.

      • Perform this operation during off-peak hours.

    • DTS validates data content but not metadata such as sequences; you must validate the metadata yourself.

    • After you switch your workloads to the destination instance, newly written sequences do not increment from the maximum value of the corresponding sequences in the source database. Before you switch your workloads, you must update the sequence values in the destination database. For more information, see Update sequence values in the destination database.

    • DTS creates the following temporary tables in the source database to obtain information such as DDL statements for incremental data, the schemas of incremental tables, and heartbeat data. Do not delete these temporary tables during migration. Otherwise, the DTS task will be disrupted. DTS automatically deletes these tables after the migration instance is released.

      public.dts_pg_class, public.dts_pg_attribute, public.dts_pg_type, public.dts_pg_enum, public.dts_postgres_heartbeat, public.dts_ddl_command, public.dts_args_session, and public.aliyun_dts_instance.

    • This limit applies to full or incremental data migration tasks where the tables to be migrated from the source database contain foreign keys, triggers, or event triggers. DTS temporarily sets the session_replication_role parameter to replica at the session level during the migration. If the destination database account does not have the required permissions, you must manually set the parameter to replica in the destination database. During this period (while session_replication_role is set to replica), cascade update or delete operations in the source database may cause data inconsistency. After the migration task is released, you can set the parameter back to origin.

    • To ensure the accuracy of the displayed latency for incremental data migration, DTS creates a heartbeat table named dts_postgres_heartbeat in the source database.

    • During incremental data migration, DTS creates a replication slot prefixed with dts_sync_ in the source database to replicate data. This replication slot allows DTS to obtain incremental logs from the source database from the last 15 minutes. When a data migration task fails or the migration instance is released, DTS attempts to automatically clean up the replication slot.

      Note

      • If you change the password of the source database account used by the task or remove the DTS IP addresses from the IP address whitelist of the source database during migration, the replication slot cannot be automatically cleaned up. In this case, you must manually clean up the replication slot in the source database to prevent log accumulation, which can exhaust disk space and cause the source database to become unavailable.

      • If a primary/secondary switchover occurs on the source database, you must log on to the secondary database to manually clean up the replication slot.

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

    • Full data migration involves concurrent INSERT operations, which can cause table fragmentation in the destination database, resulting in the destination database consuming more storage space than the source.

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

    • DTS attempts to resume a failed migration task for up to seven days. Therefore, before you switch your workloads to the destination instance, you must stop or release the task. Alternatively, revoke the write permissions of the account that DTS uses to access the destination instance by using the REVOKE command. This prevents an automatically resumed task from overwriting data in the destination instance.

    • 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.

    • When you migrate a partitioned table, you must include both the parent table and its child partitions as migration objects. Otherwise, data in the partitioned table may become inconsistent.

      Important

      • The parent table of a PostgreSQL partitioned table does not store data directly. All data is stored in its child partitions. A data migration task must include the parent table and all its child partitions. Otherwise, data in the child partitions may be missed, which leads to data inconsistency between the source and destination.

      • Migration of partitioned tables and inheritance tables (parent-child tables) across different databases is not supported. Ensure that the partitioned table and all its partitions are in the same database. Also, ensure that the parent table and all its child tables are in the same database.

    Special cases

    Do not modify the connection endpoint or zone of a source ApsaraDB RDS for PostgreSQL instance during migration, as this will cause the task to fail.

    Migration types

    • Schema migration

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

    • 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.

    Supported objects

    • schema and table

      Note

      This includes primary key, unique key, foreign key, DATATYPE (built-in data type), and default constraint.

    • view, procedure (for PostgreSQL 11 or later), function, rule, sequence, extension, trigger, aggregate, index, operator, and domain

    Supported SQL operations

    Operation type

    SQL operation

    DML

    INSERT, UPDATE, DELETE

    DDL

    • DDL migration is supported only for data migration tasks created after .

      Important

    • The migration task supports the following DDL operations, provided the source database account is a high-privilege account and the RDS PostgreSQL instance has minor engine version 20210228 or later. For information about how to upgrade the minor engine version, see Upgrade the minor engine version.

      • CREATE TABLE, DROP TABLE

      • ALTER TABLE (including RENAME TABLE, ADD COLUMN, ADD COLUMN DEFAULT, ALTER COLUMN TYPE, DROP COLUMN, ADD CONSTRAINT, ADD CONSTRAINT CHECK, and ALTER COLUMN DROP DEFAULT)

      • TRUNCATE TABLE (requires the source database to be PostgreSQL 11 or later)

      • CREATE INDEX ON TABLE

      Important

      • DDL statements that include additional information, such as CASCADE or RESTRICT, are not supported.

      • DDL statements in a session that uses the SET session_replication_role = replica command are not migrated.

      • DDL statements executed by calling a FUNCTION are not supported.

      • If a commit contains both DML and DDL operations, the DDL operations are not migrated.

      • If a commit contains DDL operations on objects that are not being migrated, those operations are not migrated.

      • DDL statements executed directly within a plugin through the SPI (Server Programming Interface) are not supported.

    Database account permissions

    Database instance

    Schema migration

    Full data migration

    Incremental data migration

    source ApsaraDB RDS for PostgreSQL instance

    The USAGE permission on the pg_catalog schema.

    The SELECT permission on the objects to be migrated.

    A privileged account that is the owner of the selected database.

    Note

    If the source ApsaraDB RDS for PostgreSQL instance runs PostgreSQL 9.4 and you need to migrate only DML operations, the account only needs the REPLICATION permission.

    destination ApsaraDB RDS for PostgreSQL instance

    The CREATE and USAGE permissions on the destination objects.

    Schema owner permissions.

    To create a database account for an ApsaraDB RDS for PostgreSQL instance and grant it permissions, see Create an account and Create a database.

    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 you select the source and destination instances, we recommend that you carefully read the limits displayed at the top of the page. Otherwise, the task may fail or data inconsistency may occur.

      Section

      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 PostgreSQL.

      Connection Type

      Select Alibaba Cloud Instance.

      Instance Region

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

      Instance ID

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

      Database Name

      Enter the name of the database in the source ApsaraDB RDS for PostgreSQL instance that contains the objects to be migrated.

      Database Account

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

      Database Password

      Enter the password for the database account.

      Encryption

      Specifies whether to encrypt the connection to the source database. You can configure this parameter based on your business requirements. In this example, Non-encrypted is selected.

      If you want to establish an SSL-encrypted connection to the source database, perform the following steps: Select SSL-encrypted, upload CA Certificate, Client Certificate, and Private Key of Client Certificate as needed, and then specify Private Key Password of Client Certificate.

      Note

      • If you set Encryption to SSL-encrypted for a self-managed PostgreSQL database, you must upload CA Certificate.

      • If you want to use the client certificate, you must upload Client Certificate and Private Key of Client Certificate and specify Private Key Password of Client Certificate.

      • For information about how to configure SSL encryption for an ApsaraDB RDS for PostgreSQL instance, see SSL encryption.

      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 PostgreSQL.

      Connection Type

      Select Alibaba Cloud Instance.

      Instance Region

      Select the region where the destination ApsaraDB RDS for PostgreSQL instance is located.

      Instance ID

      Select the ID of the destination ApsaraDB RDS for PostgreSQL instance.

      Database Name

      Enter the name of the database in the destination ApsaraDB RDS for PostgreSQL instance that will receive the migrated objects.

      Database Account

      Enter the database account for the destination ApsaraDB RDS for PostgreSQL instance. For information about the required permissions, see Permissions required for database accounts.

      Database Password

      Enter the password for the database account.

      Encryption

      Specifies whether to encrypt the connection to the source database. You can configure this parameter based on your business requirements. In this example, Non-encrypted is selected.

      If you want to establish an SSL-encrypted connection to the source database, perform the following steps: Select SSL-encrypted, upload CA Certificate, Client Certificate, and Private Key of Client Certificate as needed, and then specify Private Key Password of Client Certificate.

      Note

      • If you set Encryption to SSL-encrypted for a self-managed PostgreSQL database, you must upload CA Certificate.

      • If you want to use the client certificate, you must upload Client Certificate and Private Key of Client Certificate and specify Private Key Password of Client Certificate.

      • For information about how to configure SSL encryption for an ApsaraDB RDS for PostgreSQL instance, see 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, configure the objects that you want to migrate.

        Parameter

        Description

        Migration Types

        • To perform a one-time full data migration, select both Schema Migration and Full Data Migration.

        • To perform a migration with minimal downtime, select Schema Migration, Full Data Migration, and Incremental Data Migration.

        Note

        • If you select Schema Migration, DTS migrates the schema of the tables to be migrated, including foreign keys, from the source database to the destination database.

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

        Processing Mode of Conflicting 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.

        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

        • You can select objects at the schema or table level. If you select tables, other objects such as views, triggers, and stored procedures are not migrated.

        • If a table to be migrated contains columns of the SERIAL type and you have selected Migration Types for Schema Migration, also select Sequence or migrate the entire schema.

        Selected Objects
        Note

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

        • 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.

        • To select the incremental SQL operations to migrate at the database or table level, right-click the object in the Selected Objects box and select the desired SQL 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 based on your business requirements. This example does not require an environment tag.

        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

        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.

      3. Click Next: Data Validation to configure a data validation task.

        For more information about the data validation feature, see Configure data validation.

    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.