This topic describes how to migrate data from an Amazon Aurora MySQL database to a PolarDB for MySQL database by using Data Transmission Service (DTS). DTS supports schema migration, full data migration, and incremental data migration. When configuring a data migration task, you can select all of the supported migration types to ensure service continuity.

Prerequisites

  • The Public accessibility option of Amazon Aurora MySQL is set to Yes. This ensures that DTS can access Amazon Aurora MySQL over the Internet.
  • A PolarDB for MySQL cluster is created. For more information, see Create a PolarDB for MySQL cluster.
  • The available storage space of the PolarDB for MySQL instance is larger than the total space of the data in the Amazon Aurora MySQL instance.

Notes

  • DTS uses read and write resources of the source and destination databases during full data migration. This may increase the database load. If the database performance is unfavorable, the specification is low, or the data volume is large, database services may become unavailable. For example, DTS occupies a large amount of read and write resources in the following cases: a large number of slow SQL queries are performed on the source database, the tables have no primary keys, or a deadlock occurs in the destination database. Before you migrate data, evaluate the performance of the source and destination databases. We recommend that you migrate data during off-peak hours. For example, you can migrate data when the CPU usage of the source and destination databases is less than 30%.
  • If the source database does not have primary keys or UNIQUE constraints and fields are not required to be unique, duplicate data may exist in the destination database.
  • DTS uses the ROUND(COLUMN,PRECISION) function to retrieve values from columns of the float or double data type. If the precision is not specified, DTS sets the precision for the float data type to 38 digits and the precision for the double data type to 308 digits. You must check whether the precision settings meet your business requirements.
  • If the name of the source database is invalid, you must create a database in the PolarDB for MySQL instance before configuring a data migration task.
    Note For more information about how to create a database and the database naming conventions, see Create a database.
  • DTS automatically resumes a failed data migration task. Before switching your workloads to the destination instance, you must stop or release the data migration task. Otherwise, the data from the source database will overwrite the data in the destination instance after the task is resumed.

Billing

Migration type Migration channel fee Public network traffic fee
Schema migration or full data migration Free of charge Migrating data from Alibaba Cloud over the Internet incurs fees. For more information, see Pricing.
Incremental data migration Billed. For more information, see Pricing.

Migration types

  • Schema migration

    DTS migrates the schemas of the required objects to the PolarDB for MySQL instance. DTS supports schema migration for the following types of objects: table, view, trigger, stored procedure, and function. DTS does not support schema migration for events.

    Note
    • During schema migration, DTS changes the value of the SECURITY attribute in views, stored procedures, and functions from DEFINER to INVOKER.
    • DTS does not migrate user information. Before a user can call views, stored procedures, and functions of the destination database, you must grant the read/write permissions to the user.
  • Full data migration
    DTS migrates historical data of the required objects from the Amazon Aurora MySQL database to the destination PolarDB for MySQL database.
    Note During full data migration, concurrent INSERT operations cause segments in the tables of the destination instance. After full data migration is complete, the tablespace of the destination instance is larger than that of the source instance.
  • Incremental data migration

    After full data migration is complete, DTS retrieves binary log files from the source Amazon Aurora MySQL database. Then, DTS synchronizes incremental data from the source Amazon Aurora MySQL database to the destination PolarDB for MySQL database. Incremental data migration helps you ensure service continuity when you migrate data between MySQL databases.

Permissions required for database accounts

Database Schema migration Full data migration Incremental data migration
Amazon Aurora MySQL The permission to perform SELECT operations on the objects to be migrated The permission to perform SELECT operations on the objects to be migrated The REPLICATION SLAVE permission, REPLICATION CLIENT permission, SHOW VIEW permission, and permission to perform SELECT operations on the objects to be migrated
PolarDB for MySQL The read/write permissions for the objects to be migrated The read/write permissions for the objects to be migrated The read/write permissions for the objects to be migrated

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

Preparations before data migration

  1. Log on to the Amazon Aurora console.
  2. Go to the Basic information page of the source Amazon Aurora MySQL instance.
  3. Select the node that is set to the role of Writer.
  4. In the Connectivity & security section, click the name of the VPC security group that corresponds to the Writer node.
    Security group rules
  5. On the Security groups page, click the Inbound tab in the Security group section. On the Inbound tab, click Edit to add CIDR blocks of DTS servers in the corresponding region to the inbound rule. For more information, see Add the CIDR blocks of DTS servers to the security settings of on-premises databases.
    Edit inbound rules
    Note
    • You only need to add the CIDR blocks of DTS servers that are located in the same region as the destination database. For example, the source database is located in Singapore and the destination database is located in Hangzhou. You only need to add the CIDR blocks of DTS servers that are located in the China (Hangzhou) region.
    • You can add all the required CIDR blocks to the inbound rule at one time.
  6. Log on to the Amazon Aurora MySQL database and specify the number of hours to retain binary log files. Skip this step if you do not need to perform incremental data migration.
    call mysql.rds_set_configuration('binlog retention hours', 24);
    Note
    • The preceding command sets the retention period of binary log files to 24 hours. The maximum value is 168 hours (7 days).
    • The binary logging feature of Amazon Aurora MySQL must be enabled and the value of the binlog_format parameter must be set to row. If the version of MySQL is 5.6 or later, the value of the binlog_row_image parameter must be set to full.

Procedure

  1. Log on to the DTS console.
  2. In the left-side navigation pane, click Data Migration.
  3. At the top of Migration Tasks the page, select the region where the destination cluster resides.
    Select a region
  4. In the upper-right corner of the page, click Create Migration Task.
  5. Configure the information about the source and destination databases for the data migration task.
    Configure the source and destination databases
    Section Parameter Description
    N/A Task Name DTS automatically generates a task name. We recommend that you use an informative name for easy identification. You do not need to use a unique task name.
    Source Database Instance Type Select User-Created Database with Public IP Address.
    Instance Region If the instance type is set to User-Created Database with Public IP Address, you do not need to specify the instance region.
    Database Type Select MySQL.
    Hostname or IP Address Enter the endpoint that is used to connect to the Amazon Aurora MySQL database.
    Note You can obtain the endpoint on the Basic information page of the source Amazon Aurora MySQL instance.
    Endpoint
    Port Number Enter the service port number of the Amazon Aurora MySQL database. The default port number is 3306.
    Database Account Enter the account for the Amazon Aurora MySQL database. For more information about permissions required for the account, see #section_dsb_md9_s9i.
    Database Password Enter the password for the database account.
    Note After the source database information is specified, click Test Connectivity next to Database Password to verify whether the specified information is valid. If the specified information is valid, the Passed message appears. If the Failed message appears, click Check in the Failed message. Modify the source database information as prompted.
    Destination Database Instance Type Select PolarDB.
    Instance Region Select the region where the ApsaraDB RDS for MySQL instance resides.
    PolarDB instance ID Select the ID of the PolarDB for MySQL instance.
    Database Account Enter the database account of the PolarDB for MySQL instance. For more information about permissions required for the account, see #section_dsb_md9_s9i.
    Database Password Enter the password for the database account.
    Note After the destination database information is specified, click Test Connectivity next to Database Password to verify whether the specified information is valid. If the specified information is valid, the Passed message appears. If the Failed message appears, click Check in the Failed message. Modify the destination database information as prompted.
  6. In the lower-right corner of the page, click Set Whitelist and Next.
    Note The CIDR blocks of DTS servers are automatically added to the whitelist of the PolarDB for MySQL instance. This ensures that DTS servers can connect to the PolarDB for MySQL instance.
  7. Select the migration types and objects to be migrated.
    Select the migration types and objects to be migrated
    Parameter Description
    Migration types
    • To perform only full data migration, select Schema Migration and Full Data Migration.
    • To migrate data with minimal downtime, you must select Schema Migration, Full Data Migration, and Incremental Data Migration.
    Note If the Incremental Data Migration option is not selected, do not write new data to the Amazon Aurora MySQL instance when full data migration is in progress. Otherwise, data inconsistency may occur.
    Objects to be migrated

    In the Available section, select the objects to be migrated and click the Right arrow icon to add the objects to the Selected section.

    Note
    • You can select databases, tables, or columns as the objects to be migrated.
    • After an object is migrated to the destination instance, the name of the object remains unchanged. If you want an object to have a different name after the object is migrated to the PolarDB for MySQL instance, you can use the object name mapping feature provided by DTS. For more information about how to use this feature, see Object name mapping.
    • If you use the object name mapping feature on an object, other objects that are dependent on the object may fail to be migrated.
  8. Click Precheck on the lower right of the page.
    Note
    • A precheck is performed for a data migration task. A data migration task can be started only if it passes the precheck.
    • If the precheck fails, click Note icon corresponding to each failed item to view the details. Fix the problems as instructed and run the precheck again.
  9. After the precheck is passed, click Next.
  10. On the Confirm Settings dialog box that appears, specify Channel Specification and select the Data Transmission Service (Pay-As-You-Go) Service Terms.
  11. Click Buy and Start to start the data migration task.
    • Schema migration and full data migration

      Do not manually stop a migration task. Otherwise, data migrated to the destination database will be incomplete. Wait until the data migration task stops when it is complete.

    • Schema migration, full data migration, and incremental data migration

      An incremental data migration task does not automatically end. You must manually end the migration task.

      Note Select an appropriate time point to manually end the migration task. For example, you can end the migration task during off-peak hours or before you switch your workloads to the destination cluster.
      1. When the task progress bar switches to Incremental Data Migration and the message The migration task is not delayed appears, stop writing new data to the source database for a few minutes. Then, the progress bar will show the latency of the incremental data migration.
      2. When the status of incremental data migration changes to The migration task is not delayed, manually stop the migration task.Stop the incremental migration task
  12. Switch your workloads to the PolarDB for MySQL instance.