This topic describes how to migrate data between PolarDB for MySQL clusters by using Data Transmission Service (DTS).
- The source and destination PolarDB for MySQL clusters are created. For more information, see Purchase a pay-as-you-go cluster and Purchase a subscription cluster.
- The available storage space of the destination PolarDB for MySQL cluster is larger than the total size of the data in the source PolarDB for MySQL cluster.
|Limits on the source database||
- Schema migration
DTS migrates the schemas of the required objects from the source database to the destination database.Note
- DTS supports schema migration for the following types of objects: table, view, trigger, stored procedure, and function.
- During schema migration, DTS changes the value of the SECURITY attribute from DEFINER to INVOKER for views, stored procedures, and functions.
- DTS does not migrate user information. To call a view, stored procedure, or function of the destination database, you must grant the read and write permissions to INVOKER.
- Full data migration
DTS migrates historical data of the required 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 you to ensure service continuity when you migrate data between self-managed databases.
SQL operations that can be migrated
|Operation type||SQL statements|
|DML||INSERT, UPDATE, and DELETE|
Permissions required for database accounts
|Source PolarDB for MySQL cluster||The read permissions on the objects to be migrated|
|Destination PolarDB for MySQL cluster||The read and write permissions on the objects to be migrated|
- Go to the Data Migration page of the new DTS console.
- In the upper-left corner of the page, select the region where the data migration instance
- 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 at the top of the page. This ensures that you can create and run the data migration task.
Section Parameter Description N/A Task Name
DTS automatically generates a task name. We recommend that you specify an informative name that helps identify the task. The task name does not need to be unique.
Source Database Database Type Select PolarDB for MySQL. Access Method Select Alibaba Cloud Instance. Instance Region Select the region where the source PolarDB for MySQL cluster resides. PolarDB Cluster ID Enter the ID of the source PolarDB for MySQL cluster. Database Account Enter the database account of the source PolarDB for MySQL cluster. For information about the permissions that are required for the account, see Permissions required for database accounts. Database Password
Enter the password of the database account.
Destination Database Database Type Select PolarDB for MySQL. Access Method Select Alibaba Cloud Instance. Instance Region Select the region where the destination PolarDB for MySQL cluster resides. PolarDB Cluster ID Select the ID of the destination PolarDB for MySQL cluster. Database Account Enter the database account of the destination PolarDB for MySQL cluster. For information about the permissions that are required for the account, see Permissions required for database accounts. Database Password
Enter the password of the database account.
- In the lower part of the page, click Test Connectivity and Proceed.
- Select objects for the task and configure advanced settings.
- Basic Settings
Parameter Description Task Stages
Note If Incremental Data Migration is not selected, we recommend that you do not write data to the source instance during data migration. This ensures data consistency between the source and destination instances.
- To perform only full data migration, select Schema Migration and Full Data Migration.
- To ensure service continuity during data migration, select Schema Migration, Full Data Migration, and Incremental Data Migration.
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
identical table names, the precheck is passed. Otherwise, an error is returned during
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 identical table names and the tables in the destination database cannot be deleted or renamed.
- 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 migrate data records that have the same primary keys as data records in the destination database.
- If the source and destination databases have different schemas, only some columns are migrated or the data migration task fails.
Select one or more objects from the Source Objects section and click the icon to move the objects to the Selected Objects section.Note You can select columns, tables, or databases 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, and stored procedures to the destination database.
Rename Databases and Tables
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 rename an object that you want to migrate to the destination instance, right-click the object in the Selected Objects section.
- To rename multiple objects at a time, click in the upper-right corner of the Selected Objects section.
You can specify WHERE conditions to filter data. For more information, see Use SQL conditions to filter data.
Select the SQL operations to be migrated In the Selected Objects section, right-click an object. In the dialog box that appears, select the DDL and DML operations that you want to migrate. For more information, see SQL operations that can be migrated.
- Advanced Settings
Parameter Description Set AlertsSpecify whether to set alerts for the data migration task. If the task fails or the migration latency exceeds the threshold, the alert contacts will receive notifications.
- Select No if you do not want to set alerts.
- Select Yes to set alerts. In this case, you must also set the alert threshold and alert contacts.
Replicate Temporary Tables When DMS Performs DDL OperationsIf you use Data Management (DMS) to perform online DDL operations on the source database, you can specify whether to migrate temporary tables generated by online DDL operations.
- Yes: DTS migrates the data of temporary tables generated by online DDL operations.
Note If online DDL operations generate a large amount of data, the migration task may be delayed.
- No: DTS does not migrate the data of temporary tables generated by online DDL operations.
Only the original DDL data of the source database is migrated.
Note If you select No, the tables in the destination database may be locked.
Retry Time for Failed ConnectionsSpecify the retry time for failed connections. Valid values: 10 to 1440. Unit: minutes. Default value: 120. We recommend that you set the retry time to more than 30 minutes. If DTS reconnects to the source and destination databases within the specified time, DTS resumes the data migration task. Otherwise, the data migration task fails.Note
- If multiple DTS instances have the same source or destination database, the lowest value takes effect. For example, the retry time is set to 30 minutes for Instance A and 60 minutes for Instance B, DTS retries failed connections at an interval of 30 minutes.
- 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.
- Basic Settings
- In the lower part of the page, click Next: Precheck and Start 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, you can click the icon next to each failed item to view details.
- You can troubleshoot the issues based on the causes and run a precheck again.
- If you do not need to troubleshoot the issues, you can ignore failed items and run a precheck again.
- Wait until the Success Rate becomes 100%. Then, click Next: Purchase Instance.
- On the Purchase Instance page, specify the Instance Class parameter for the data migration instance. The following
table describes the parameter.
Section Parameter Description Parameters Instance Class
DTS provides several instance classes that have different performance in migration speed. You can select an instance class based on your business scenario. For more information, see Specifications of data migration instances.
- Read and select Data Transmission Service (Pay-as-you-go) Service Terms.
- Click Buy and Start to start the data migration task. You can view the progress of the task in the task list.