Data Transmission Service:Synchronize data from a PolarDB-X 1.0 instance to an AnalyticDB for MySQL cluster

Precautions

• DTS uses read and write resources of the source and destination databases during initial full data synchronization. This may increase the loads of the database servers. If the database performance or specifications are unfavorable, 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 synchronize data, evaluate the impact of data synchronization on the performance of the source and destination databases. We recommend that you synchronize data during off-peak hours. For example, you can synchronize data when the CPU utilization of the source and destination databases is less than 30%.
• When the data synchronization task is running, do not upgrade or downgrade the PolarDB-X instance, migrate frequently-accessed tables, change shard keys, or perform DDL operations on source objects. Otherwise, the data synchronization task fails.
• If you need to change the network type of a PolarDB-X instance during data synchronization, you must modify the network connection information of the data synchronization task after you complete the network type change.
• We recommend that you do not use gh-ost or pt-online-schema-change to perform DDL operations on the required objects during data synchronization. Otherwise, data may fail to be synchronized.
• Due to the limits of AnalyticDB for MySQL, if the disk space usage of the nodes in an AnalyticDB for MySQL cluster reaches 80%, the cluster is locked. We recommend that you estimate the required disk space based on the objects to be synchronized. You must make sure that the destination cluster has sufficient storage space.
• Prefix indexes cannot be synchronized. If the source database contains prefix indexes, data may fail to be synchronized.

SQL operations that can be synchronized

INSERT, UPDATE, and DELETE

Permissions required for database accounts

Data type mappings

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

Procedure

1. Purchase a data synchronization instance. For more information, see Purchase a DTS instance.
   Note On the buy page, set Source Instance to PolarDB-X, Target Instance to AnalyticDB for MySQL, and Synchronization Topology to One-Way Synchronization.
2. Log on to the DTS console.
   Note If you are redirected to the Data Management (DMS) console, you can click the icon in the lower-right corner to go to the previous version of the DTS console.
3. In the left-side navigation pane, click Data Synchronization.
4. In the upper part of the Data Synchronization Tasks page, select the region in which the destination instance resides.
5. Find the data synchronization instance and click Configure Task in the Actions column.
6. Configure the source and destination instances.
   

   Section	Parameter	Description
   N/A	Synchronization Task Name	The task name that DTS automatically generates. We recommend that you specify a descriptive name that makes it easy to identify the task. You do not need to use a unique task name.
   Source Instance Details	Instance Type	This parameter is set to DRDS Instance and cannot be changed.
   	Instance Region	The source region that you selected on the buy page. The value of this parameter cannot be changed.
   	DRDS Instance ID	The ID of the source PolarDB-X 1.0 instance.
   Destination Instance Details	Instance Type	This parameter is set to AnalyticDB and cannot be changed.
   	Instance Region	The destination region that you selected on the buy page. The value of this parameter cannot be changed.
   	Version	Select 3.0.
   	Database	The ID of the AnalyticDB for MySQL instance.
   	Database Account	The database account of the AnalyticDB for MySQL cluster. 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.

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

   • You do not need to modify the security settings for ApsaraDB instances (such as ApsaraDB RDS for MySQL and ApsaraDB for MongoDB) and ECS-hosted databases. DTS automatically adds the CIDR blocks of DTS servers to the whitelists of ApsaraDB instances or the security group rules of Elastic Compute Service (ECS) instances. For more information, see Add the CIDR blocks of DTS servers to the security settings of on-premises databases.
   • After data synchronization is complete, we recommend that you remove the CIDR blocks of DTS servers from the whitelists or security groups.
8. Select the synchronization policy and objects to synchronize.
   

   Setting	Description
   Initial Synchronization	You must select both Initial Schema Synchronization and Initial Full Data Synchronization in most cases. After the precheck is complete, DTS synchronizes the schemas and data of required objects from the source instance to the destination cluster. The schemas and data are the basis for subsequent incremental synchronization.
   Processing Mode In Existed Target Table	Pre-check and Intercept: checks whether the destination database contains tables that have the same names as tables in the source database. If the destination database does not contain tables that have the same names as those in the source database, the precheck is passed. Otherwise, an error is returned during precheck and the data synchronization task cannot be started. Note If the source and destination databases contain identical table names and the tables in the destination database cannot be deleted or renamed, you can use the object name mapping feature to rename the tables that are synchronized to the destination database. For more information, see Rename an object to be synchronized. 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 consistency is not guaranteed and your business may be exposed to potential risks. If the source and destination databases have the same schema, DTS does not synchronize data records that have the same primary keys as data records in the destination database. If the source and destination databases have different schemas, initial data synchronization may fail. In this case, only part of columns are synchronized, or the data synchronization task fails.
   Merge Multi Tables	If you select Yes, DTS adds the __dts_data_source column to each table to record data sources. No is selected by default. Note If you set this parameter to Yes, all of the selected source tables in the task are merged into a destination table. If you want to merge only part of the source tables, you can create two data synchronization tasks.
   Synchronization Type	Select the types of operations that you want to synchronize based on your business requirements. All operation types are selected by default. Insert Update Delete
   Select the objects to synchronize	Select one or more tables from the Available section and click the icon to add the tables to the Selected section. Note You can select only tables as objects to synchronize. You can use the object name mapping feature to rename the columns that are synchronized to the destination database. For more information, see Rename an object to be synchronized.
   Rename Databases and Tables	You can use the object name mapping feature to rename the objects that are synchronized to the destination instance. For more information, see Object name mapping.
   Retry Time for Failed Connections	By default, if DTS fails to connect to the source or destination database, DTS retries within the next 720 minutes (12 hours). You can specify the retry time based on your needs. If DTS reconnects to the source and destination databases within the specified time, DTS resumes the data synchronization task. Otherwise, the data synchronization task fails. Note When DTS retries a connection, you are charged for the DTS instance. We recommend that you specify the retry time based on your business needs. You can also release the DTS instance at your earliest opportunity after the source and destination instances are released.

9. In the lower-right corner of the page, click Next.
10. Specify a type for the tables that you want to synchronize to the destination database.
    

    Note After you select Initial Schema Synchronization, you must specify the type, primary key column, and partition key column for the tables that you want to synchronize to the destination AnalyticDB for MySQL cluster. For more information, see CREATE TABLE.
11. In the lower-right corner of the page, click Precheck.
    Note

    • Before you can start the data synchronization task, DTS performs a precheck. You can start the data synchronization task only after the task passes the precheck.
    • If the task fails to pass the precheck, click the icon next to each failed item to view details.
      • After you troubleshoot the issues based on the causes, run a precheck again.
      • If you do not need to troubleshoot the issues, ignore failed items and run a precheck again.
12. Close the Precheck dialog box after the following message is displayed: Precheck Passed. Then, the data synchronization task starts.
13. Wait until initial synchronization is complete and the data synchronization task enters the Synchronizing state.
    You can view the status of the data synchronization task on the Synchronization Tasks page.