This topic describes how to migrate full data from a self-managed TiDB database to an ApsaraDB RDS for MySQL instance by using Data Transmission Service (DTS).
Prerequisites
Notice
- The destination ApsaraDB RDS for MySQL instance must reside in the China (Hangzhou), China (Shanghai), China (Qingdao), China (Beijing), China (Shenzhen), China (Zhangjiakou), China (Hong Kong), Singapore (Singapore), US (Silicon Valley), or US (Virginia) region.
- The available storage space of the destination ApsaraDB RDS for MySQL instance must be larger than the total size of the data in the self-managed TiDB database.
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. |
Migration types
| Migration type | Description |
|---|---|
| Schema migration | DTS migrates the schemas of the required objects to the destination database. DTS
supports schema migration for views, tables, and databases.
Warning TiDB and MySQL are heterogeneous databases. DTS does not ensure that the schemas of
the source and destination databases are consistent after schema migration. We recommend
that you evaluate the impact of data type conversion on your business. For more information,
see Data type mappings between heterogeneous databases.
|
| Full data migration | DTS migrates historical data of the required objects to the destination database.
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.
|
Before you begin
If a whitelist is configured for the TiDB database, you must add the CIDR blocks of DTS servers to the whitelist of the database. For more information, see Add the CIDR blocks of DTS servers to the security settings of on-premises databases.
Procedure
- Configure the source and destination databases.
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 an instance type based on the deployment of the source database. In this example, select User-Created Database in ECS Instance. Note If you select other instance types, you must deploy the network environment for the source database. For more information, see Preparation overview.Instance Region Select the region of the Elastic Compute Service (ECS) instance on which the source TiDB database is deployed. Database Type Select TiDB. Port Number Enter the service port number of the source TiDB database. The default port number is 4000. Database Account Enter the account of the source TiDB database. The account must have the SELECT permission on the objects to be migrated and the SHOW VIEW permission. Database Password Enter the password of the database account. Notice 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 RDS Instance. Instance Region Select the region where the destination RDS instance resides. RDS Instance ID Select the ID of the destination RDS instance. Database Account Enter the database account of the destination RDS instance. The account must have the read and write permissions on the destination database. For more information about how to create and authorize a database account, see Create an account on an ApsaraDB RDS for MySQL instance and Modify the permissions of a standard account for an ApsaraDB RDS for MySQL instance. Database Password Enter the password of the database account. Notice 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.Encryption Select Non-encrypted or SSL-encrypted. If you want to select SSL-encrypted, you must enable SSL encryption for the RDS instance before you configure the data migration task. For more information, see Configure SSL encryption on an ApsaraDB RDS for MySQL instance. Notice The Encryption parameter is available only for regions in mainland China and the China (Hong Kong) region. - Select the migration types and the objects to be migrated.
Setting Description Select the migration types Select both Schema Migration and Full Data Migration. For more information about migration types, see Migration types. Notice To ensure data consistency, we recommend that you do not write data to the source TiDB database during data migration.Select the objects to be migrated Select one or more objects from the Available section and click the
icon to add the objects to the Selected section.
Notice- You can select columns, tables, or databases as the objects to be migrated.
- By default, after an object is migrated to the destination database, the name of the object remains unchanged. You can use the object name mapping feature to change the names of the objects that are migrated to the destination database. For more information, see Object name mapping.
- If you use the object name mapping feature on an object, other objects that are dependent on the object may fail to be migrated.
Specify whether to rename object names You can use the object name mapping feature to change the names of the objects that are migrated to the destination instance. For more information, see Object name mapping. Specify the retry time for failed connections to the source or destination database By default, if DTS fails to connect to the source or destination database, DTS retries within the next 12 hours. You can specify the retry time based on your needs. 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 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. - In the lower-right corner of the page, click Precheck. Note
- Before you can start the data migration task, a precheck is performed. 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.
- Click Buy and Start to start the data migration task. Warning We recommend that you do not manually stop a task during full data migration. Otherwise, the data migrated to the destination database will be incomplete. You can wait until the data migration task automatically stops.
