Apsara PolarDB is a next-generation relational database service developed by Alibaba Cloud. It is a high-performance, high-availability, easy-to-use, and reliable service that is compatible with the MySQL database engine. This topic describes how to migrate data between Apsara PolarDB for MySQL clusters that are owned by different Alibaba Cloud accounts by using Data Transmission Service (DTS).
Prerequisites
- The source and destination Apsara PolarDB for MySQL clusters are created. For more information, see Create a PolarDB MySQL cluster.
- The binary logging feature is enabled for the source Apsara PolarDB for MySQL cluster. For more information, see Enable binlogging.
Background information
- 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 your ApsaraDB RDS for MySQL database does not have primary key or unique constraints and each field in the database has duplicate values, the data migrated to the destination database may be duplicated.
- If a data migration task fails, DTS attempts to resume the task. In this case, before you switch your workloads to the destination database, you must stop or release the task. Otherwise, the data in the source database will overwrite the data in the destination database after the task is resumed.
Migration types
DTS supports schema migration, full data migration, and incremental data migration.
For more information, see Terms.
Note You can use these three migration types together to migrate data without service interruptions.
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. |
SQL operations that can be synchronized during incremental data migration
| Operation type | SQL statements |
|---|---|
| DML | INSERT, UPDATE, DELETE, and REPLACE |
| DDL |
|
Permissions required for database accounts
| Database | Required permission |
|---|---|
| Source Apsara PolarDB for MySQL cluster | The read permission on the objects to be migrated |
| Destination Apsara PolarDB for MySQL cluster | The read/write permissions on the objects to be migrated |
Note For more information about how to create and authorize a database account, see Create database accounts.
Preparations
Procedure
- At the top of Migration Tasks the page, select the region where the destination cluster resides.
- Select User-Created Database Connected over Express Connect, VPN Gateway, or Smart Access
Gateway as the instance type. Then, click Proprietary network of Other Apsara Stack Accounts next to the Peer VPC field.
Note To migrate data between Apsara PolarDB for MySQL clusters across Alibaba Cloud accounts, you can specify the source Apsara PolarDB for MySQL cluster as a user-created database connected over Express Connect. You can also request a public endpoint for the source Apsara PolarDB for MySQL cluster and specify the source cluster as a user-created database with a public IP address.
- Configure the source and destination databases for 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 for easy identification. You do not need to use a unique task name. Source Database Instance Type Select User-Created Database Connected over Express Connect, VPN Gateway, or Smart Access Gateway. Instance Region Select the region where the source PolarDB cluster resides. Alibaba Cloud Account ID Enter the ID of the Alibaba Cloud account to which the source PolarDB cluster belongs. Note To obtain the ID of the Alibaba Cloud account to which the source PolarDB cluster belongs, you must log on to the Account Management console by using this account. The account ID is displayed on the Security Settings page.
Role Name Enter the name of the RAM role that you created earlier in Preparations. Peer VPC Select the ID of the VPC where the source PolarDB cluster resides. To obtain the VPC ID, you must log on to the Apsara PolarDB console by using the Alibaba Cloud account to which the source PolarDB cluster belongs. On the Clusters page, click the ID of the source PolarDB cluster. The VPC ID is displayed in the Basic Information section.
Database Type Select MySQL. IP Address Enter the private IP address of the source PolarDB cluster. In this example, enter 172.16.20.20. You can obtain the private IP address by pinging the VPC-facing endpoint of the source PolarDB cluster.
Port Number Enter the service port number of the source PolarDB cluster. The default port number is 3306. Database Account Enter the database account of the source PolarDB cluster. For more information about the permissions that are required for the account, see Permissions required for database accounts. Database Password Enter the password of the source database account. Note After you specify the source database parameters, click Test Connectivity next to Database Password to verify whether the specified parameters are valid. If the specified parameters are valid, the Passed message appears. If the Failed message appears, click Check next to Failed. Modify the source database parameters based on the check results.Destination Database Instance Type Select PolarDB. Instance Region Select the region where the destination PolarDB cluster resides. PolarDB Instance ID The ID of the destination PolarDB cluster. Database Account Enter the database account of the destination PolarDB cluster. For more information about the permissions that are required for the account, see Permissions required for database accounts. Database Password Enter the password of the destination database account. Note After you specify the destination database parameters, click Test Connectivity next to Database Password to verify whether the parameters are valid. If the specified parameters are valid, the Passed message appears. If the Failed message appears, click Check next to Failed. Modify the destination database parameters based on the check results. - Configure migration types and objects.
Item Description Migration types - To perform only full data migration, select Schema Migration and Full Data Migration.
- If you want to migrate data without business disruptions, select Schema Migration, Full Data Migration, and Incremental Data Migration.
Note If Incremental Data Migration is not selected, do not write data into the source database during full data migration. This ensures data consistency between the source and destination databases.Objects to be migrated Select the objects to be migrated in the Available section and click
icon to move them to the Selected section.
Note- Objects to be migrated can be databases, tables, or columns.
- By default, the selected objects are not renamed after the migration. If you want to rename the objects that are migrated to the destination 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 for an object, objects that depend on the object may fail to be migrated.
- 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
icon corresponding to each failed item to view the details. Fix the problems as instructed
and run the precheck again.
- 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.- 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.
- When the status of incremental data migration changes to The migration task is not delayed, manually stop the migration task.
- Schema migration and full data migration
icon to move them to the 
icon corresponding to each failed item to view the details. Fix the problems as instructed
and run the precheck again.
What to do next
The database accounts that are used for data migration have the read/write permissions. After the data migration is complete, you must delete the database accounts to ensure security.