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Data Transmission Service:Migrate data from a PolarDB-X 2.0 instance to an AnalyticDB for PostgreSQL instance

Last Updated:Jul 07, 2023

This topic describes how to migrate data from a PolarDB-X 2.0 instance to an AnalyticDB for PostgreSQL instance by using Data Transmission Service (DTS).

Prerequisites

  • The source PolarDB-X 2.0 instance is created. For more information, see Create PolarDB-X instances.
  • The destination AnalyticDB for PostgreSQL instance is created. For more information, see Create an instance.
  • The available storage space of the destination AnalyticDB for PostgreSQL instance is larger than the total size of the data in the source PolarDB-X 2.0 instance.

Limits

CategoryDescription
Limits on the source database
  • The tables to be migrated must have PRIMARY KEY or UNIQUE constraints, and all fields must be unique. Otherwise, the destination database may contain duplicate data records.
  • If you select tables as the objects to be migrated and you need to modify the tables in the destination database, such as renaming tables or columns, you can migrate up to 1,000 tables in a single data migration task. If you run a task to migrate more than 1,000 tables, a request error occurs. In this case, we recommend that you configure multiple tasks to migrate the tables in batches or configure a task to migrate the entire database.
  • If you need to migrate incremental data, make sure that the following requirements are met:
    • The binary logging feature is enabled. The value of the binlog_row_image parameter is set to full. Otherwise, error messages are returned during precheck and the data migration task cannot be started.
    • If you perform only incremental data migration, the binary logs of the source database must be stored for more than 24 hours. If you perform full data migration and incremental data migration, the binary logs of the source database must be stored for at least seven days. Otherwise, Data Transmission Service (DTS) may fail to obtain the binary logs and the task may fail. In exceptional circumstances, data inconsistency or loss may occur. After full data migration is complete, you can set the retention period to more than 24 hours. Make sure that you set the retention period of binary logs based on the preceding requirements. Otherwise, the Service Level Agreement (SLA) of DTS does not guarantee service reliability or performance.

  • Limits on operations:
    • During data migration, do not upgrade or downgrade the source instance, migrate frequently-updated tables, change shard keys, or perform DDL operations on source objects. Otherwise, the data migration task fails.
    • During full data migration and incremental data migration, DTS temporarily disables the constraint check and cascade operations on foreign keys at the session level. If you perform the cascade and delete operations on the source database during data migration, data inconsistency may occur.
    • If you change the network type of the PolarDB-X 2.0 instance during data migration, you must also modify the network connection information of the data migration task.
    • If you perform only full data migration, do not write data to the source database during data migration. Otherwise, data inconsistency may occur between the source and destination databases. To ensure data consistency, we recommend that you select schema migration, full data migration, and incremental data migration as the migration types.
Other limits
  • Before you migrate data, evaluate the impact of data migration on the performance of the source and destination databases. We recommend that you migrate data during off-peak hours. During full data migration, DTS uses the read and write resources of the source and destination databases. This may increase the loads on the database servers.
  • DTS attempts to resume data migration tasks that failed within the last seven days. Before you switch workloads to the destination database, you must stop or release the failed tasks. You can also execute the REVOKE statement to revoke the write permissions from the accounts that are used by DTS to access the destination database. Otherwise, the data in the source database overwrites the data in the destination database after a failed task is resumed.
Usage notes

DTS updates the `dts_health_check`.`ha_health_check` table in the source database as scheduled to move forward the binary log file position.

Billing

Migration typeInstance configuration feeInternet traffic fee
Schema migration and full data migrationFree of charge. Free of charge
Incremental data migrationCharged. For more information, see Billing overview.

Migration types

  • Schema migration

    Data Transmission Service (DTS) migrates the schemas of objects from the source database to the destination database.

  • Full data migration

    DTS migrates the existing data of objects from the source database to the destination database.

  • Incremental data migration

    After full data migration is complete, DTS migrates incremental data from the source database to the destination database. Incremental data migration allows data to be migrated smoothly without interrupting services of self-managed applications during data migration.

SQL operations that can be incrementally migrated

Operation typeSQL statement
DMLINSERT, UPDATE, and DELETE

Permissions required for database accounts

DatabaseSchema migrationFull data migrationIncremental data migration
PolarDB-X 2.0 instanceSELECT permissionSELECT permissionREPLICATION SLAVE and REPLICATION CLIENT permissions, and SELECT permission on the objects to be migrated
Note For more information about how to grant the permissions to the database account, see Data synchronization tools for PolarDB-X.
AnalyticDB for PostgreSQL instanceRead and write permissions

Data type mappings

For more information, see Data type mappings for schema synchronization.

Procedure

  1. Go to the Data Migration Tasks page.
    1. Log on to the Data Management (DMS) console.
    2. In the top navigation bar, click DTS.
    3. In the left-side navigation pane, choose DTS (DTS) > Data Migration.
    Note
  2. From the drop-down list next to Data Migration Tasks, select the region in which the data migration instance resides.
    Note If you use the new DTS console, you must select the region in which the data migration instance resides in the upper-left corner.
  3. Click Create Task. On the page that appears, configure the source and destination databases.
    Warning After you select the source and destination instances, we recommend that you read the instructions in the Limits section that is displayed in the upper part of the page. This helps you create and run the data migration task.
    SectionParameterDescription
    N/ATask Name

    The name of the task. DTS automatically generates a task name. We recommend that you specify a descriptive name for easy identification. You do not need to specify a unique task name.

    Source DatabaseSelect Instance
    Select whether to use an existing instance.
    • If you select an existing instance, DTS automatically applies the parameter settings of the instance. You do not need to configure the corresponding parameters again.
    • If you do not use an existing instance, you must configure parameters for the source database.
    Database TypeThe type of the source database. Select PolarDB-X 2.0.
    Access MethodThe access method of the source database. Select Alibaba Cloud Instance.
    Instance RegionThe region in which the source PolarDB-X 2.0 instance resides.
    Replicate Data Across Alibaba Cloud AccountsSpecifies whether to migrate data across Alibaba Cloud accounts. In this example, No is selected.
    Instance IDThe ID of the source PolarDB-X 2.0 instance.
    Database AccountThe database account of the source PolarDB-X 2.0 instance. For information about the permissions that are required for the account, see the Permissions required for database accounts section of this topic.
    Database Password

    The password of the database account.

    Destination DatabaseSelect Instance
    Select whether to use an existing instance.
    • If you select an existing instance, DTS automatically applies the parameter settings of the instance. You do not need to configure the corresponding parameters again.
    • If you do not use an existing instance, you must configure parameters for the source database.
    Database TypeThe type of the destination database. Select AnalyticDB for PostgreSQL.
    Access MethodThe access method of the destination database. Select Alibaba Cloud Instance.
    Instance RegionThe region in which the destination AnalyticDB for PostgreSQL instance resides.
    Database AccountThe database account of the destination AnalyticDB for PostgreSQL instance.
    Database Password

    The password of the database account.

  4. In the lower part of the page, click Test Connectivity and Proceed.
    If the source or destination database is an Alibaba Cloud database instance, such as an ApsaraDB RDS for MySQL or ApsaraDB for MongoDB instance, DTS automatically adds the CIDR blocks of DTS servers to the whitelist of the instance. If the source or destination database is a self-managed database hosted on an Elastic Compute Service (ECS) instance, DTS automatically adds the CIDR blocks of DTS servers to the security group rules of the ECS instance, and you must make sure that the ECS instance can access the database. If the source or destination database is a self-managed database that is deployed in a data center or provided by a third-party cloud service provider, you must manually add the CIDR blocks of DTS servers to the whitelist of the database to allow DTS to access the database. For more information about the CIDR blocks of DTS servers, see Add the CIDR blocks of DTS servers to the security settings of on-premises databases.
    Warning If the CIDR blocks of DTS servers are automatically or manually added to the whitelist of a database or an instance, or to the security group rules of an ECS instance, security risks may arise. Therefore, before you use DTS to migrate data, you must understand and acknowledge the potential risks and take preventive measures, including but not limited to the following measures: enhance the security of your username and password, limit the ports that are exposed, authenticate API calls, regularly check the whitelist or ECS security group rules and forbid unauthorized CIDR blocks, or connect the database to DTS by using Express Connect, VPN Gateway, or Smart Access Gateway.
  5. Configure the objects to be migrated and advanced settings.
    ParameterDescription
    Migration Type
    • If you want to perform only full data migration, select Schema Migration and Full Data Migration.
    • To ensure service continuity during data migration, select Schema Migration, Full Data Migration, and Incremental Data Migration.
    Note
    • If Schema Migration is selected, the foreign keys in the source database are also migrated to the destination database.
    • If Full Data Migration is selected, you can migrate the schema of and data in the tables that are created by using the CREATE TABLE statement to the destination database.
    • If Incremental Data Migration is not selected, we recommend that you do not write data to the source database during data migration. This ensures data consistency between the source and destination databases.
    Processing Mode of Conflicting Tables
    • Precheck and Report Errors: checks whether the destination database contains tables that have the same names as tables in the source database. If the source and destination databases do not contain identical table names, the precheck is passed. Otherwise, an error is returned during the precheck and the data migration task cannot be started.

      Note You can use the object name mapping feature to rename the tables that are migrated to the destination database. You can use this feature if the source and destination databases contain tables that have identical names and the tables in the destination database cannot be deleted or renamed. For more information, see Map object names.
    • Ignore Errors and Proceed: skips the precheck for identical table names in the source and destination databases.
      Warning If you select Ignore Errors and Proceed, data inconsistency may occur, and your business may be exposed to potential risks.
      • If the source and destination databases have the same schema, DTS does not migrate data records that have the same primary keys as data records in the destination database.
      • If the source and destination databases have different schemas, only some columns are migrated or the data migration task fails. Proceed with caution.
    Capitalization of Object Names in Destination InstanceThe capitalization of database names, table names, and column names in the destination instance. By default, the DTS default policy is selected. You can select other options to make sure that the capitalization of object names is consistent with that in the source or destination database. For more information, see Specify the capitalization of object names in the destination instance.
    Source Objects

    Select one or more objects from the Source Objects section. Click the Rightwards arrow icon and add the objects to the Selected Objects section.

    Note
    • You can select columns, tables, or databases as the objects to be migrated. If you select tables as the objects to be migrated, DTS does not migrate other objects such as views, triggers, or stored procedures to the destination database.
    • If you select a database as the object to be migrated, DTS migrates data based on the following default rules:
      • If the table to be migrated in the source database has a primary key, such as a single-column primary key or a composite primary key, the primary key columns are specified as the distribution keys.
      • If the table to be migrated in the source database does not have a primary key, an auto-increment primary key column is automatically generated in the destination table. This may cause data inconsistency between the source and destination databases.
    Selected Objects
    • To rename an object that you want to migrate to the destination instance, right-click the object in the Selected Objects section. For more information, see Map the name of a single object.
    • To rename multiple objects at a time, click Batch Edit in the upper-right corner of the Selected Objects section. For more information, see Map multiple object names at a time.
    Note
    • If you use the object name mapping feature to rename an object, other objects that are dependent on the object may fail to be migrated.
    • To specify WHERE conditions to filter data, right-click a table in the Selected Objects section. In the dialog box that appears, specify the conditions. For more information, see Use SQL conditions to filter data.
    • To select the SQL operations performed on a specific database or table, right-click an object in the Selected Objects section. In the dialog box that appears, select the SQL operations that you want to migrate. For more information about the SQL operations that can be migrated, see the SQL operations that can be incrementally migrated section of this topic.
  6. Click Next: Advanced Settings to configure advanced settings.
    ParameterDescription
    Set Alerts
    Specifies whether to set alerts for the data migration task. If the task fails or the migration latency exceeds the threshold, the alert contacts will receive notifications. Valid values:
    Retry Time for Failed Connections
    The retry time range for failed connections. If the source or destination database fails to be connected after the data migration task is started, DTS immediately retries a connection within the time range. Valid values: 10 to 1440. Unit: minutes. Default value: 720. We recommend that you set the parameter to a value greater than 30. If DTS reconnects to the source and destination databases within the specified time range, DTS resumes the data migration task. Otherwise, the data migration task fails.
    Note
    • If you set different retry time ranges for multiple data migration tasks that have the same source or destination database, the shortest retry time range that is set takes precedence.
    • When DTS retries a connection, you are charged for the DTS instance. We recommend that you specify the retry time range based on your business requirements. You can also release the DTS instance at your earliest opportunity after the source and destination instances are released.
    The wait time before a retry when other issues occur in the source and destination databases
    The retry time range for other issues. For example, if the DDL or DML operations fail to be performed after the data migration task is started, DTS immediately retries the operations within the time range. Valid values: 1 to 1440. Unit: minutes. Default value: 10. We recommend that you set the parameter to a value greater than 10. If the failed operations are successfully performed within the specified time range, DTS resumes the data migration task. Otherwise, the data migration task fails.
    Important The value of the The wait time before a retry when other issues occur in the source and destination databases parameter must be smaller than the value of the Retry Time for Failed Connections parameter.
    Configure ETL
    Specifies whether to configure the extract, transform, and load (ETL) feature. For more information, see What is ETL?. Valid values:
    Whether to delete SQL operations on heartbeat tables of forward and reverse tasks
    Specifies whether to write SQL operations on heartbeat tables to the source database while the DTS instance is running.
    • Yes: does not write SQL operations on heartbeat tables. In this case, a latency of the DTS instance may be displayed.
    • No: writes SQL operations on heartbeat tables. In this case, specific features such as physical backup and cloning of the source database may be affected.
  7. Click Next: Configure Database and Table Fields. On the page that appears, configure the primary key columns and distribution keys of the tables that you want to migrate to the destination AnalyticDB for PostgreSQL instance.
    Note
    • If you select Schema Migration as Migration Types, you must configure the parameters such as Type, Primary Key Column, and Distribution Key for the tables that you want to migrate to the destination AnalyticDB for PostgreSQL instance. For more information, see CREATE TABLE.
    • In the Primary Key Column field, you can specify multiple columns to form a composite primary key. In this case, you must specify one or more primary key columns as the distribution keys.
  8. In the lower part of the page, click Next: Save Task Settings and Precheck.
    Note
    • Before you can start the data migration task, DTS performs a precheck. You can start the data migration task only after the task passes the precheck.
    • If the task fails to pass the precheck, click View Details next to each failed item. After you troubleshoot the issues based on the causes, run a precheck again.
    • If an alert is triggered for an item during the precheck:
      • If an alert item cannot be ignored, click View Details next to the failed item and troubleshoot the issues. Then, run a precheck again.
      • If an alert item can be ignored, click Confirm Alert Details. In the View Details dialog box, click Ignore. In the message that appears, click OK. Then, click Precheck Again to run a precheck again. If you ignore the alert item, data inconsistency may occur, and your business may be exposed to potential risks.
  9. Wait until the Success Rate value becomes 100%. Then, click Next: Purchase Instance.
  10. On the Purchase Instance page, specify the Instance Class parameter for the data migration instance. The following table describes the parameter.
    SectionParameterDescription
    ParametersInstance Class

    DTS provides several instance classes that vary in the migration speed. You can select an instance class based on your business scenario. For more information, see Specifications of data migration instances.

  11. Read and select the check box to agree to Data Transmission Service (Pay-as-you-go) Service Terms.
  12. Click Buy and Start to start the data migration task. You can view the progress of the task in the task list.