PolarDB:Synchronize PolarDB for MySQL to AnalyticDB for MySQL

Limitations

• During initial full data synchronization, DTS consumes read and write resources from the source and destination databases, which increases the database load. If database performance is poor, instance specifications are low, or business traffic is heavy (for example, the source database has many slow SQL queries or tables without primary keys, or the destination database experiences deadlocks), the database load increases and may even cause the service to become unavailable. Before you synchronize data, evaluate the performance of your source and destination instances. We recommend performing data synchronization during off-peak hours, for example, when the CPU utilization of both instances is below 30%.

• Do not use gh-ost or pt-online-schema-change for DDL operations on source objects during synchronization. Otherwise, the task fails.

• In AnalyticDB for MySQL, a cluster is locked when any node's disk usage exceeds 80%. Ensure the destination cluster has sufficient capacity before starting.

• Tables with prefix indexes cannot be synchronized and may cause task failure.

• If the destination AnalyticDB for MySQL 3.0 cluster is backing up while the DTS task runs, the task fails.

Billing

Supported SQL operations

• DDL operations: CREATE TABLE, DROP TABLE, RENAME TABLE, TRUNCATE TABLE, ADD COLUMN, DROP COLUMN, MODIFY COLUMN

• DML operations: INSERT, UPDATE, DELETE

Database account permissions

For more information about how to create and authorize a database account, see Create a PolarDB for MySQL database account or Create a database account for Cloud-native Data Warehouse AnalyticDB for MySQL.

Data type mappings

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

Procedure

1. Purchase a data synchronization task.

   Note

   When purchasing the task, set Source Instance to Apsara PolarDB, Target Instance to AnalyticDB MySQL, and Synchronization Topology to One-way synchronization.

2. 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.

3. In the left-side navigation pane, click Data Synchronization.

4. At the top of the Synchronization Tasks page, select the region where your destination instance is located.

5. Find the data synchronization task that you purchased and click Configure Task.

6. Configure the source and destination instances for the synchronization channel.

   Section	Parameter	Description
   N/A	Synchronization task name	DTS automatically generates a task name. For easy identification, we recommend using a descriptive name. The name does not need to be unique.
   Source instance details	Instance type	Set to PolarDB Instance. This parameter cannot be changed.
   	Instance region	The region of the source instance that you selected when you purchased the task. This parameter cannot be changed.
   	PolarDB instance ID	Select the ID of the source PolarDB for MySQL cluster.
   	Database account	Enter the database account for the PolarDB for MySQL cluster. For information about the required permissions, see Database account permissions.
   	Database password	Enter the password for the database account.
   Destination instance details	Instance type	Set to ADS. This parameter cannot be changed.
   	Instance region	The region of the destination instance that you selected when you purchased the task. This parameter cannot be changed.
   	Version	Select 3.0.
   	Database	Select the cluster ID of the destination AnalyticDB for MySQL instance.
   	Database account	Enter the database account for the AnalyticDB for MySQL instance. For information about the required permissions, see Database account permissions.
   	Database password	Enter the password for the database account.

7. In the lower-right corner of the page, click Set Whitelist and Next.

   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 Whitelist DTS server IP addresses.

   Warning

   Adding the public IP address blocks of the DTS service, either automatically or manually, may pose security risks. Using this product, you acknowledge that you understand and accept the potential security risks and that you must implement basic security measures. These measures include, but are not limited to, strengthening password security, limiting the ports open to each CIDR block, using authentication for internal API calls, and regularly checking and restricting unnecessary CIDR blocks. Alternatively, you can connect through a private network using a leased line, VPN Gateway, or Smart Access Gateway.

8. Configure the synchronization policy and objects.

   Parameter	Description
   Synchronization initialization	By default, both Initial schema synchronization and Initial full data synchronization are selected. After the precheck is complete, DTS initializes the schema and data of the synchronized objects in the destination cluster. This process creates a baseline for subsequent incremental data synchronization.
   Action on existing tables in destination	Precheck and report error: Checks if a table with the same name exists in the destination database. If no such table exists, the check passes. If a table with the same name exists, an error is reported during the precheck phase, and the data synchronization task will not start. Note If you cannot delete or rename the conflicting table in the destination database, you can map the table to a new name in the destination. For more information, see Set object names in the destination instance. Ignore Errors and Proceed: Skips the check for tables with the same name in the destination database. Warning Selecting Ignore Errors and Proceed can lead to data inconsistencies and business risks. For example: If a record in the destination cluster has the same primary key as a source record, the destination record is kept, and the source record is not synchronized. If the table schemas are different, the data might not initialize, only some columns might be synchronized, or the task might fail.
   Merge multiple tables	Select Yes: DTS adds the __dts_data_source column to each table to store the data source and no longer supports DDL synchronization. No: The default option. DDL synchronization is supported. Note The table merge feature is applied at the task level, not the table level. If you need to merge some tables but not others, create two separate data synchronization tasks.
   Synchronization operation types	Select the operation types to synchronize. For more information about supported operations, see Supported SQL operations. By default, all operation types are selected.
   Select synchronization objects	In the Available objects box, click the objects you want to synchronize, and then click the icon to move them to the Selected objects box. You can select databases and tables as synchronization objects. Note If you select an entire database, all schema change operations for objects within that database are synchronized to the destination. If you select a specific table, only ADD COLUMN operations on that table are synchronized to the destination. By default, the names of the synchronization objects remain the same. If you need to change the object names in the destination cluster, use the object name mapping feature. For more information, see Set object names in the destination instance.
   Rename object mappings	Change the names of synchronized objects in the destination instance. For more information, see Map databases, tables, and columns.
   Replicate temporary tables during online DDL process in DMS	If you use Data Management (DMS) to perform online DDL changes on the source database, you can choose whether to synchronize the temporary tables generated by the DDL changes. Yes: Synchronizes the temporary tables generated by online DDL changes. Note If a large amount of temporary table data is generated by online DDL changes, the data synchronization task may be delayed. No: Does not synchronize the temporary tables generated by online DDL changes. Only the original DDL operations from the source database are synchronized. Note This option causes tables in the destination database to be locked.
   Connection retry timeout	If DTS cannot connect to the source or destination instance, it retries for 720 minutes (12 hours) by default. You can also specify a custom retry duration. If DTS reconnects to the source or destination instance within the specified duration, the synchronization task automatically resumes. Otherwise, the task fails. Note You are billed for task run time during connection retries. Customize the retry duration based on your business needs, or release the DTS instance as soon as the source and destination instances are released.

9. After you complete the preceding configurations, click Next in the lower-right corner of the page.

10. Specify the table properties in the destination database.

    The configuration table also includes the ADB Table Group, ADB Table Name, Number of Partitions, and Definition Status columns. You can hover over a table or database name to view its original name in the source database.

    Note

    If you selected Initial Schema Synchronization, define the Type, primary key column, partition key column, and other properties for tables in AnalyticDB for MySQL. CREATE TABLE.

11. After completing the preceding configurations, click Precheck and Start in the lower-right corner of the page.

    Note

    • A precheck runs before the synchronization task starts, and you can only start the task after it passes.

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

      • You can fix the issues based on the cause and run the precheck again.

      • If you do not need to fix the items that triggered warnings, you can click Ignore or Ignore Warnings and Rerun Precheck to skip the warnings and run the precheck again.

12. After the Precheck dialog box displays Precheck Passed, close the Precheck dialog box. The synchronization task starts automatically.

13. Wait for the task to finish initialization and enter the Synchronizing state.

    You can view the status of the data synchronization task on the Data Synchronization page.