PolarDB is a next-generation relational database service that is developed by Alibaba Cloud. PolarDB is compatible with the MySQL database engine and features high availability, ease of use, and reliability. This topic describes how to migrate data between PolarDB for MySQL clusters by using Data Transmission Service (DTS).
Note A PolarDB for MySQL cluster of an earlier version cannot be upgraded to 8.0. However,
you can create a PolarDB for MySQL cluster of version 8.0, and then migrate data to
this cluster. Before you migrate data between different versions of PolarDB for MySQL
clusters, we recommend that you create a pay-as-you-go PolarDB cluster to test the
compatibility. After testing, you can release the cluster.
Prerequisites
- The source and destination PolarDB for MySQL clusters are created. For more information, see Create a PolarDB for MySQL cluster.
- The binary logging feature is enabled for the source PolarDB for MySQL cluster. For more information, see Enable binary logging.
Precautions
- DTS uses read and write resources of the source and destination databases during full data migration. This may increase the loads of the database servers. 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 impact of data migration on 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 utilization of the source and destination databases is less than 30%.
- The source database must have PRIMARY KEY or UNIQUE constraints and all fields must be unique. Otherwise, the destination database may contain duplicate data records.
- If a data migration task fails, DTS automatically resumes the task. Before you switch your workloads to the destination database, stop or release the data migration 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 When you migrate data between PolarDB for MySQL clusters, you can select all of the
supported migration types to ensure service continuity.
Billing
Migration type | Task configuration fee | Internet traffic fee |
---|---|---|
Schema migration and full data migration | Free of charge. | Charged only when data is migrated from Alibaba Cloud over the Internet. For more information, see Pricing. |
Incremental data migration | Charged. 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 permissions |
---|---|
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 |
Note For more information about how to create and authorize a database account, see Create a database account.
Procedure
What to do next
The database accounts that are used for data migration have the read and write permissions. After data migration is complete, you must delete the database accounts to ensure security.