This topic describes how to migrate data from a user-created MySQL database that is connected over Express Connect, VPN Gateway, or Smart Access Gateway to an ApsaraDB RDS for MySQL instance by using Data Transmission Service (DTS). In this scenario, the Express Connect circuit and the destination RDS instance are owned by different Alibaba Cloud accounts. DTS supports schema migration, full data migration, and incremental data migration. You can select all of the supported migration types to ensure service continuity.
Prerequisites
- The version of the user-created MySQL database is 5.1, 5.5, 5.6, 5.7, or 8.0.
- The available storage space of the destination ApsaraDB RDS for MySQL instance is larger than the total size of the data in the user-created MySQL database.
- The on-premises network to which the user-created MySQL database belongs is connected
to Alibaba Cloud VPC over Express Connect, VPN Gateway, or Smart Access Gateway. The
Express Connect circuit and the destination RDS instance are owned by different Alibaba
Cloud accounts.
Note For more information about how to connect an on-premises data center to a VPC, see Connect to local IDCs.
Background information

Precautions
- 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%.
- The source database must have PRIMARY KEY or UNIQUE constraints and all fields must be unique. Otherwise, duplicate data may exist in the destination database.
- DTS uses the
ROUND(COLUMN,PRECISION)
function to retrieve values from columns of the float or double data type. If the precision is not specified, DTS sets the precision for the float data type to 38 digits and the precision for the double data type to 308 digits. You must check whether the precision settings meet your business requirements. - DTS automatically creates a destination database in the ApsaraDB RDS for MySQL instance.
However, if the name of the source database is invalid, you must manually create a
database in the ApsaraDB RDS for MySQL instance before you configure the data migration
task.
Note For more information about how to create a database and the database naming conventions, see Create databases and accounts.
- DTS automatically resumes a failed data migration 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.
Billing
Migration type | Instance configurations | Internet traffic |
---|---|---|
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. |
Migration types
- Schema migration
DTS migrates the schemas of the required objects to the destination instance. DTS supports schema migration for the following types of objects: table, view, trigger, stored procedure, and function.
Note- During schema migration, DTS changes the value of the SECURITY attribute in views, stored procedures, and functions from DEFINER to INVOKER.
- DTS does not migrate user information. Before a user can call views, stored procedures, and functions of the destination database, you must grant the read/write permissions to the user.
- Full data migration
DTS migrates historical data of the required objects from the user-created MySQL database to the destination database in the ApsaraDB RDS for MySQL instance.Note During full data migration, concurrent INSERT operations cause fragmentation in the tables of the destination instance. After full data migration is complete, the tablespace of the destination instance is larger than that of the source database.
- Incremental data migration
After full data migration is complete, DTS retrieves binary log files from the user-created MySQL database. Then, DTS synchronizes incremental data from the user-created MySQL database to the destination ApsaraDB RDS for MySQL instance. Incremental data migration allows you to ensure service continuity when you migrate data from a user-created MySQL database to Alibaba Cloud.
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 | Schema migration | Full data migration | Incremental data migration |
---|---|---|---|
User-created MySQL database | The SELECT permission | The SELECT permission | The REPLICATION SLAVE, REPLICATION CLIENT, SHOW VIEW, and SELECT permissions |
ApsaraDB RDS for MySQL instance | The read/write permissions | The read/write permissions | The read/write permissions |
For more information about how to create and authorize a database account, see the following topics:
Preparations
- Create an account for a user-created MySQL database and configure binary logging.
- Log on to the Alibaba Cloud console by using the Alibaba Cloud account to which the Express Connect circuit belongs. Authorize DTS to access the network that is connected over Express Connect. For more information, see Configure a route between DTS and Express Connect, VPN Gateway, or Smart Access Gateway.
- Create a RAM role and authorize this role to access the cloud resources of the Alibaba Cloud account to which the Express Connect circuit belongs. For more information, see Configure RAM authorization for data migration from a user-created database in a VPC across different Alibaba Cloud accounts.