This topic describes how to migrate data from a self-managed MySQL database that is connected over Express Connect, VPN Gateway, or Smart Access Gateway to an ApsaraDB RDS for MySQL database by using Data Transmission Service (DTS). DTS supports schema migration, full data migration, and incremental data migration. When you migrate data from a self-managed MySQL database, you can select all of the supported migration types to ensure service continuity.
Prerequisites
- The version of the self-managed MySQL database is 5.1, 5.5, 5.6, 5.7, or 8.0.
- The available storage space of the ApsaraDB RDS for MySQL instance is larger than the total size of the data in the self-managed MySQL database.
- The on-premises network to which the self-managed MySQL database belongs is connected
to Alibaba Cloud over Express Connect, VPN Gateway, or Smart Access Gateway.
Note For more information, see Connect an on-premises database to Alibaba Cloud.
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 tables to be migrated in 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.
- DTS uses the
ROUND(COLUMN,PRECISION)
function to retrieve values from columns of the FLOAT or DOUBLE data type. If you do not specify a precision, 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 the naming conventions of ApsaraDB RDS for MySQL databases and how to create a database, see Create a database on an ApsaraDB RDS for MySQL instance.
- If a data migration task fails, DTS automatically resumes the task. Before you switch your workloads to the destination instance, stop or release the data migration task. Otherwise, the data in the source database will overwrite the data in the destination instance after the task is resumed.
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. |
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 from DEFINER to INVOKER for views, stored procedures, and functions.
- 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 and write permissions to the user.
- Full data migration
DTS migrates historical data of the required objects from the self-managed 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 database. After full data migration is complete, the tablespace of the destination database is larger than that of the source database.
- Incremental data migration
After full data migration is complete, DTS retrieves binary log files from the self-managed MySQL database. Then, DTS synchronizes incremental data from the self-managed 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 self-managed 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 |
---|---|---|---|
Self-managed 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 and write permissions | The read and write permissions | The read and write permissions |
For more information about how to create and authorize a database account, see the following topics:
- Self-managed MySQL database: Create an account for a user-created MySQL database and configure binary logging
- ApsaraDB RDS for MySQL instance: Create an account on an ApsaraDB RDS for MySQL instance and Modify the permissions of a standard account on an ApsaraDB RDS for MySQL instance.