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Data Transmission Service:Migrate data from an ApsaraDB RDS for MySQL instance to a PolarDB-X 1.0 instance

Last Updated:Apr 03, 2024

This topic describes how to migrate data from an ApsaraDB RDS for MySQL instance to a PolarDB-X 1.0 instance by using Data Transmission Service (DTS).

Supported source databases

You can use DTS to migrate data from the following types of MySQL databases to a PolarDB-X 1.0 instance. In this example, an ApsaraDB RDS for MySQL instance is used. You can also follow the procedure to configure data migration tasks for other types of MySQL databases.

  • ApsaraDB RDS for MySQL instance

  • Self-managed databases:

    • Self-managed database with a public IP address
    • 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

Prerequisites

Limits

Category

Description

Limits on the source database

  • Bandwidth requirements: The server to which the source database belongs must have sufficient outbound bandwidth. Otherwise, the data migration speed is affected.

  • 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, up to 1,000 tables can be migrated 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 want to migrate incremental data, make sure that the following requirements are met:

    • The binary logging feature is enabled. The binlog_format parameter is set to row. The binlog_row_image parameter is set to full. Otherwise, error messages are returned during the precheck and the data migration task cannot be started.

      Important
      • If the source database is a self-managed MySQL database deployed in a dual-primary cluster, you must set the log_slave_updates parameter to ON. This ensures that DTS can obtain all binary logs.

      • By default, the binary logging feature is enabled for an ApsaraDB RDS for MySQL instance.

    • 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 both full data migration and incremental data migration, the binary logs of the source database must be stored for at least seven days. Otherwise, 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 to be performed on the source database:

    • During full data migration, do not perform DDL operations to change the schemas of databases or tables. Otherwise, the data migration task fails.

    • 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 full data migration and incremental data migration as the migration types.

Other limits

  • The storage type of the PolarDB-X instance must be ApsaraDB RDS for MySQL, which refers to custom ApsaraDB RDS for MySQL instances. PolarDB for MySQL cannot be used as the storage type.

  • Schema migration is not supported. Before you configure a data migration task, you must create databases and tables in the destination instance based on the databases and tables that you want to migrate.

  • 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.

  • During full data migration, concurrent INSERT operations cause fragmentation in the tables of the destination database. After full data migration is complete, the tablespace of the destination database is larger than that of the source database.

  • You must make sure that the precision settings for columns of the FLOAT or DOUBLE data type meet your business requirements. DTS uses the ROUND(COLUMN,PRECISION) function to retrieve values from columns of the FLOAT or DOUBLE data type. If you do not specify a precision, DTS sets the precision for the FLOAT data type to 38 digits and the precision for the DOUBLE data type to 308 digits.

  • DTS attempts to resume data migration tasks that failed within the last seven days. Before you switch workloads to the destination database, 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.

Special cases

If the source database is a self-managed MySQL database, take note of the following limits:

  • If you perform a primary/secondary switchover on the source database when the data migration task is running, the task fails.

  • DTS calculates migration latency based on the timestamp of the latest migrated data in the destination database and the current timestamp in the source database. If no DML operation is performed on the source database for an extended period of time, the migration latency may be inaccurate. If the latency of the data migration task is too high, you can perform a DML operation on the source database to update the latency.

    Note

    If you select an entire database as the object to be migrated, you can create a heartbeat table. The heartbeat table is updated or receives data every second.

  • DTS executes the CREATE DATABASE IF NOT EXISTS `test` statement in the source database as scheduled to move forward the binary log file position.

Billing

Migration type

Instance configuration fee

Internet traffic fee

Full data migration

Free of charge.

Charged only when data is migrated from Alibaba Cloud over the Internet. For more information, see Billing overview.

Incremental data migration

Charged. For more information, see Billing overview.

Migration types

  • 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 the services of self-managed applications during data migration.

SQL operations that can be incrementally migrated

Operation type

SQL statement

DML

INSERT, UPDATE, and DELETE

Permissions required for database accounts

Database

Full data migration

Incremental data migration

ApsaraDB RDS for MySQL instance

SELECT permission

REPLICATION SLAVE, REPLICATION CLIENT, SHOW VIEW, and SELECT permissions

PolarDB-X 1.0 instance

Read and write permissions

For more information about how to create a database account and grant permissions to the database account, see the following topics:

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 limits displayed in the upper part of the page. This helps you create and run the data migration task.

    Section

    Parameter

    Description

    N/A

    Task Name

    The name of the task. DTS automatically assigns a name to the task. We recommend that you specify a descriptive name that makes it easy to identify the task. You do not need to specify a unique task name.

    Source Database

    Select an existing DMS database instance

    The database instance that you want to use. You can determine whether to select an existing instance based on your business requirements.

    • If you select an existing instance, DTS automatically populates the parameters for the instance.

    • If you do not select an existing instance, you must configure parameters for the source database.

    Database Type

    The type of the source database. Select MySQL.

    Access Method

    The access method of the source database. Select Alibaba Cloud Instance.

    Instance Region

    The region in which the source ApsaraDB RDS for MySQL instance resides.

    Replicate Data Across Alibaba Cloud Accounts

    Specifies whether to migrate data across Alibaba Cloud accounts. In this example, No is selected.

    RDS Instance ID

    The ID of the source ApsaraDB RDS for MySQL instance.

    Database Account

    The database account of the source ApsaraDB RDS for MySQL instance. For information about the permissions that are required for the account, see Permissions required for database accounts.

    Database Password

    The password of the database account.

    Encryption

    Specifies whether to encrypt the connection to the source database. You can select Non-encrypted or SSL-encrypted based on your business requirements. If you select SSL-encrypted, you must enable SSL encryption for the ApsaraDB RDS for MySQL instance before you configure the data migration task. For more information, see Configure the SSL encryption feature.

    Destination Database

    Select an existing DMS database instance

    The database instance that you want to use. You can determine whether to select an existing instance based on your business requirements.

    • If you select an existing instance, DTS automatically populates the parameters for the instance.

    • If you do not select an existing instance, you must configure parameters for the destination database.

    Database Type

    The type of the destination database. Select PolarDB-X 1.0.

    Access Method

    The access method of the destination database. Select Alibaba Cloud Instance.

    Instance Region

    The region in which the destination PolarDB-X 1.0 instance resides.

    Instance ID

    The ID of the destination PolarDB-X 1.0 instance.

    Database Account

    The database account of the destination PolarDB-X 1.0 instance. For information about the permissions that are required for the account, see Permissions required for database accounts.

    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 IP address 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 self-managed database is hosted on multiple ECS instances, you must manually add the CIDR blocks of DTS servers to the security group rules of each ECS instance. 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 IP address whitelist of the database to allow DTS to access the database. For more information, see the "CIDR blocks of DTS servers" section of the Add the CIDR blocks of DTS servers topic.

    Warning

    If the public CIDR blocks of DTS servers are automatically or manually added to the IP address whitelist of a database 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: enhancing the security of your account and password, limiting the ports that are exposed, authenticating API calls, regularly checking the IP address whitelist or ECS security group rules and forbidding unauthorized CIDR blocks, and connecting the database to DTS by using Express Connect, VPN Gateway, or Smart Access Gateway.

  5. Configure the objects to be migrated and advanced settings.

    Parameter

    Description

    Migration Types

    • To perform only full data migration, select only Full Data Migration.

    • To ensure service continuity during data migration, select Full Data Migration and Incremental Data Migration.

    Note

    If you do not select Incremental Data Migration, 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 tables that have 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 table 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 the following potential risks:

      • If the source and destination databases have the same schemas, DTS does not migrate data records that have the same primary key values as data records in the destination database.

      • If the source and destination databases have different schemas, only specific columns are migrated or the data migration task fails. Proceed with caution.

    Capitalization of Object Names in Destination Instance

    The capitalization of database names, table names, and column names in the destination instance. By default, 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 and click the 向右小箭头 icon to add the objects to the Selected Objects section.

    Note

    You can select columns, tables, or schemas as the objects to be migrated. If you select tables or columns as the objects to be migrated, DTS does not migrate other objects, such as views, triggers, or stored procedures, to the destination database.

    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 an object in the Selected Objects section. In the dialog box that appears, specify the conditions. For more information, see Set filter conditions.

    • To select the DDL or DML 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 DML or DDL operations that you want to migrate. For more information about the DML and DDL operations that can be migrated, see SQL operations that can be incrementally migrated.

  6. Click Next: Advanced Settings.

    Parameter

    Description

    Set Alerts

    Specifies whether to configure alerting for the data migration task. If the task fails or the migration latency exceeds the specified threshold, the alert contacts will receive notifications. Valid values:

    • No: does not configure alerting.

    • Yes: configures alerting. If you select Yes, you must also specify the alert threshold and alert contacts. For more information, see Configure monitoring and alerting.

    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 retry 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 is reconnected to the source and destination databases within the specified retry time range, DTS resumes the data migration task. Otherwise, the data migration task fails.

    Note
    • If you specify different retry time ranges for multiple data migration tasks that share the same source or destination database, the value that is specified later 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.

    Configure ETL

    Specifies whether to configure the extract, transform, and load (ETL) feature. For more information about ETL, see What is ETL?

  7. In the lower part of the page, click Next: Save Task Settings and Precheck.

    You can move the pointer over Next: Save Task Settings and Precheck and click Preview OpenAPI parameters to view the parameters to be specified when you call the relevant API operation to configure the DTS task.

    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 error message, you can run a precheck again.

    • If an alert is triggered for an item during the precheck:

      • If the alert item cannot be ignored, click View Details next to the failed item and troubleshoot the issues. Then, run a precheck again.

      • If the 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.

  8. Wait until the success rate becomes 100%. Then, click Next: Purchase Instance.

  9. On the Purchase Instance page, configure the Instance Class parameter for the data migration instance. The following table describes the parameters.

    Section

    Parameter

    Description

    New Instance Class

    Resource Group

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

    Instance Class

    DTS provides 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.

  10. Read and agree to Data Transmission Service (Pay-as-you-go) Service Terms by selecting the check box.

  11. Click Buy and Start to start the data migration task. You can view the progress of the task in the task list.