Data Transmission Service:Migrate ApsaraDB RDS for MySQL to PolarDB for MySQL

Usage notes

• During a full data migration, DTS consumes read and write resources on the source and destination databases, increasing their load. If your databases have poor performance, low specifications, or high workloads (for example, if the source database has many slow SQL queries or tables without primary keys, or if deadlocks occur in the destination database), the increased load can strain your databases or even cause service interruptions. Perform the data migration during off-peak hours, such as when the CPU utilization of both databases is below 30%.

• If a source table has no primary key, unique constraint, or any field combination that ensures uniqueness, DTS may generate duplicate data in the destination.
• Full data migration uses concurrent INSERT operations, which cause table fragmentation. After migration, the destination tablespace is larger than the source.
• DTS automatically recovers failed tasks. Before switching workloads to the destination, stop or release the task to prevent it from overwriting destination data.
• The rate of full data migration cannot be adjusted.

Limitations

• DTS supports schema migration for tables, views, triggers, stored procedures, and stored functions.
  Note During schema migration, DTS changes the DEFINER for views, stored procedures, or functions to INVOKER.
• DTS does not migrate user information. To call views, stored procedures, or functions in the destination, grant read and write permissions to the caller.

Migration types

Billing

SQL operations for incremental migration

Required database account permissions

Procedure

1. Log on to the DTS console.

   Note

   If you are automatically redirected to the Data Management (DMS) console, you can click the icon in the lower-right corner and then click to return to the classic DTS console.

2. In the left-side navigation pane, click Data Migration.

3. At the top of the Migration Tasks page, select the region of the destination cluster.

4. In the upper-right corner of the page, click Create Data Migration Task.

5. Configure the connection settings for the source and destination databases.

   Category	Parameter	Description
   N/A	Task name	Auto-generated by DTS. You can specify a descriptive name for easier identification. The name does not need to be unique.
   Source database	Instance type	Select RDS Instance.
   	Instance region	Select the region of the source RDS for MySQL instance.
   	Database account	Enter the database account of the source RDS for MySQL instance. Required database account permissions.
   	Database password	Enter the database account password. Note After configuring the source database, click Database Password next to Test Connectivity to test the connection. On success, a Passed message appears. On failure, a Failed message appears. Click Failed next to the Diagnose message and fix the issue as prompted.
   	Connection method	Select Non-encrypted or SSL-encrypted based on your requirements. If you select SSL-encrypted, enable SSL encryption for the RDS instance first. Configure SSL encryption. Note The Encryption parameter is available only in the Chinese mainland and China (Hong Kong) regions.
   Destination database	Instance type	Select PolarDB.
   	Instance region	Select the region of the destination PolarDB for MySQL cluster.
   	PolarDB instance ID	Select the destination PolarDB for MySQL cluster ID.
   	Database account	Enter the database account of the destination PolarDB for MySQL cluster. Required database account permissions.
   	Database password	Enter the database account password. Note After configuring the destination database, click Database Password next to Test Connectivity to test the connection. On success, a Passed message appears. On failure, a Failed message appears. Click Failed next to the Diagnose message and fix the issue as prompted.

6. After configuration, click Add to whitelist and continue.

   If the source or destination is an Alibaba Cloud database instance, such as ApsaraDB for MySQL or ApsaraDB for MongoDB, DTS automatically adds the IP addresses of its servers in the corresponding region to the instance's whitelist. If the source or destination is a self-managed database on an ECS instance, DTS automatically adds its IP addresses to the security rules of the ECS instance. You must also ensure that the self-managed database does not restrict access from the ECS instance. If the database is a cluster deployed across multiple ECS instances, you must manually add the DTS IP addresses to the security rules for each ECS instance. If the source or destination is a database in an on-premises data center or on another cloud, you must manually add the DTS IP addresses for the corresponding region to allow access from DTS servers. For a list of DTS server IP addresses, see DTS server IP addresses.

   Warning

   Adding the public CIDR blocks of DTS servers, whether automatically or manually, may introduce security risks. By using this product, you acknowledge and accept these potential risks. You are responsible for implementing basic security measures, including but not limited to using strong passwords, restricting open ports, using authentication for internal API calls, regularly reviewing and restricting unnecessary network segments, or connecting through private networks such as Express Connect, VPN Gateway, or Smart Access Gateway.

7. Select the migration types and objects.

   Setting	Description
   Migration types	To perform only a full migration, select both Schema Migration and Full Data Migration. To perform a zero-downtime migration, select Schema Migration, Full Data Migration, and Incremental Data Migration. Important If you do not select Incremental Data Migration, do not write new data to the source database during the full data migration to ensure data consistency.
   Migration objects	In the Available box, click the objects that you want to migrate and click the icon to move them to the Selected Objects box. Important You can select objects to migrate at the database, table, and column levels. By default, object names are retained after migration. If you need to rename an object in the destination database, use the object name mapping feature. For more information, see Object name mapping. If you rename an object by using the object name mapping feature, other objects that depend on it may fail to migrate.
   Object name mapping	If you need to rename a migrated object in the destination instance, use the object name mapping feature. For more information, see Object name mapping.
   Connection retry duration	If a connection to the source or destination database is interrupted, DTS retries to connect for a default of 720 minutes (12 hours). You can customize this duration. If DTS successfully reconnects within the specified time, the migration task resumes. Otherwise, the task fails. Note You are charged for the DTS instance while it attempts to reconnect. To avoid unnecessary charges, set an appropriate retry duration or release the DTS instance promptly if the source and destination databases are released.
   Replicate temporary tables created during online DDL operations in DMS	If you use Data Management (DMS) to perform online DDL operations on the source database, you can choose whether to migrate the temporary tables that are generated. Yes: Migrates the data in the temporary tables that are generated by online DDL operations. Note If a large amount of temporary table data is generated by online DDL operations, the migration task may experience high latency. No: Does not migrate the data in the temporary tables. Only the original DDL data from the source database is migrated. Note This option may cause table locks on the destination database.

8. After you complete the configuration, click Precheck and Start in the lower-right corner of the page.

   Note

   • Before the migration task starts, DTS runs a precheck. The task can start only after it passes the precheck.

   • If the precheck fails, click the icon next to the failed item to view details.

     • Fix the issues as prompted and run the precheck again.

     • If you do not need to fix the warning items, you can select Ignore and then click Ignore Warnings and Rerun Precheck to run the precheck again.

9. After the task passes the precheck, click Next.

10. In the Confirm Settings dialog box that appears, select a Instance Class and select the Data Transmission Service (pay-as-you-go) Service Terms checkbox.

11. Click Buy and Start to begin the migration.

    • Schema migration + Full data migration

      Allow the task to complete automatically. Stopping it manually may result in incomplete data.

    • Schema migration + Full data migration + Incremental data migration

      The migration task does not stop automatically. You must stop it manually.

      Important

      Choose an appropriate time to stop the task manually, such as during off-peak hours or when you are ready to switch your business to the destination cluster.

      1. Wait until the migration task enters the Incremental Data Migration phase and the status shows Undelayed. Then, stop writing data to the source database for several minutes. During this time, the status of Incremental Data Migration may show a latency.

      2. Wait for the Incremental Data Migration status to show Undelayed again. Then, manually stop the migration task. Select the check box of the target migration task, and click Pause in the batch operation bar at the bottom of the page.

12. Switch your business to the PolarDB for MySQL cluster.