Data Transmission Service:Migrate data from a self-managed MySQL database to an ApsaraDB RDS for MySQL instance

Prerequisites

• An ApsaraDB RDS for MySQL instance is created. For more information, see An ApsaraDB RDS for MySQL instance is created. For more information, see Create an ApsaraDB RDS for MySQL instance..

• The engine 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 destination ApsaraDB RDS for MySQL instance is larger than the total size of the data in the self-managed MySQL database.

Limits

• 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 database naming conventions of ApsaraDB RDS for MySQL databases and how to create a database, see Manage databases.

• 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 overwrites the data in the destination instance after the task is resumed.

Billing rules

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. To call a view, stored procedure, or function of the destination database, you must grant the read and write permissions to INVOKER.

• 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

Permissions required for database accounts

For information about how to create and authorize a database account, see the following topics:

• Self-managed MySQL databases: Create an account for a self-managed MySQL database and configure binary logging

• RDS MySQL instance: Create an account on an ApsaraDB RDS for MySQL instance and Modify the permissions of an account.

Before you begin

Create an account for a self-managed MySQL database and configure binary logging

Procedure

1. Log on to the DTS console.

   Note

   If you are redirected to the Data Management (DMS) console, you can click the icon in the to go to the previous version of the DTS console.

2. In the left-side navigation pane, click Data Migration.

3. In the upper part of the Migration Tasks page, select the region in which the RDS instance resides.

4. In the upper-right corner of the page, click Create Migration Task.

5. Configure the self-managed Oracle database and the ApsaraDB RDS for MySQL instance.

   Section	Parameter	Description
   N/A	Task Name	DTS automatically generates a task name. We recommend that you specify an informative name to identify the task. You do not need to specify a unique task name.
   Source Database	Instance Type	The instance type of the source database. You can select an instance type based on the deployment of the source database. In this example, User-Created Database with Public IP Address is selected. Note If you select other instance types, you must deploy the network environment for the self-managed database. For more information, see Preparation overview.
   	Instance Region	The region in which the source database resides. If you select User-Created Database with Public IP Address as the instance type, you do not need to specify the Instance Region parameter. Note If a whitelist is configured for the self-managed MySQL database, you must manually add the CIDR blocks of DTS servers to the whitelist of the database. You can click Get IP Address Segment of DTS next to Instance Region to obtain the CIDR blocks of DTS servers.
   	Database Type	The type of the source database. In this example, MySQL is selected.
   	Hostname or IP Address	The endpoint that is used to connect to the self-managed MySQL database. In this example, the public IP address is used.
   	Port Number	The service port number of the self-managed MySQL database. The port must be accessible over the Internet. The default port number is 3306.
   	Database Account	The account of the self-managed MySQL database. For more information about the permissions that are required for the account, see the Permissions required for database accounts section of this topic.
   	Database Password	The password of the database account. Note After you specify the information about the source database, you can click Test Connectivity next to Database Password to check whether the information is valid. If the information is valid, the Passed message appears. If the Failed message appears, click Check next to Failed. Then, modify the information based on the check results.
   Destination Database	Instance Type	The instance type of the destination database. Select RDS Instance.
   	Instance Region	The region in which the destination ApsaraDB RDS for MySQL instance resides.
   	RDS Instance ID	The ID of the destination ApsaraDB RDS for MySQL instance.
   	Database Account	The database account of the ApsaraDB RDS for MySQL instance. For more information about the permissions that are required for the account, see the Permissions required for database accounts section of this topic.
   	Database Password	The password of the database account. Note After you specify the information about the RDS instance, you can click Test Connectivity next to Database Password to check whether the information is valid. If the information is valid, the Passed message appears. If the Failed message appears, click Check next to Failed. Then, modify the information based on the check results.
   	Encryption	Specifies whether to encrypt the connection to the destination instance. Select Non-encrypted or SSL-encrypted. If you select SSL-encrypted, you must enable SSL encryption for the ApsaraDB RDS for MySQL instance before you configure the data migration task. For more information, see Configure SSL encryption for an ApsaraDB RDS for MySQL instance. Note The Encryption parameter is available only for regions in the Chinese mainland and the China (Hong Kong) region.

6. In the lower-right corner of the page, click Set Whitelist and Next.

   If the source or destination database instance is an Alibaba Cloud database instance, such as an ApsaraDB RDS for MySQL or ApsaraDB for MongoDB instance, or is a self-managed database hosted on Elastic Compute Service (ECS), DTS automatically adds the CIDR blocks of DTS servers to the whitelist of the database instance or ECS security group rules. If the source or destination database is a self-managed database on data centers or is from other cloud service providers, you must manually add the CIDR blocks of DTS servers to allow DTS to access the database. For more information about the CIDR blocks of DTS servers, see the "CIDR blocks of DTS servers" section of the Add the CIDR blocks of DTS servers to the security settings of on-premises databases topic.

   Warning

   If the CIDR blocks of DTS servers are automatically or manually added to the whitelist of the database or instance, or to the ECS security group rules, security risks may arise. Therefore, before you use DTS to migrate data, you must understand and acknowledge the potential risks and take preventive measures, including but not limited to the following measures: enhance the security of your username and password, limit the ports that are exposed, authenticate API calls, regularly check the whitelist or ECS security group rules and forbid unauthorized CIDR blocks, or connect the database to DTS by using Express Connect, VPN Gateway, or Smart Access Gateway.

7. Select the objects to be migrated and the migration types.

   Parameter or setting	Description
   Select the migration types	To perform only full data migration, select Schema Migration and Full Data Migration. To ensure service continuity during data migration, select Schema Migration, Full Data Migration, and Incremental Data Migration. Note If Incremental Data Migration is not selected, do not write data to the source database during data migration. This ensures data consistency between the source and destination databases.
   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. Note You can select columns, tables, or databases as the objects to be migrated. If you select tables or columns as the objects to be migrated, DTS does not migrate other objects such as views, triggers, or stored procedures to the destination database. 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 rename the objects that are migrated to the destination database. For more information, see Object name mapping. If you use the object name mapping feature to rename an object, other objects that are dependent on the object may fail to be migrated.
   Specify whether to rename objects	You can use the object name mapping feature to rename the objects that are migrated to the destination instance. For more information, see Object name mapping.
   Specify the retry time range 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 following 12 hours. You can specify the retry time range based on your business requirements. If DTS is reconnected to the source and destination databases within the specified time range, 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 requirements. You can also release the DTS instance at your earliest opportunity after the source and destination instances are released.
   Specify whether to copy temporary tables to the destination database when DMS performs online DDL operations on the source table	If you use DMS to perform online DDL operations on the source database, you can specify whether to migrate temporary tables generated by online DDL operations. Yes: DTS migrates the data of temporary tables generated by online DDL operations. Note If online DDL operations generate a large amount of data, latency may occur for the data migration task. No: DTS does not migrate the data of temporary tables generated by online DDL operations. Only the original DDL data of the source database is migrated. Note If you select No, the tables in the destination database may be locked.

8. Click Precheck.

   Note

   • A precheck is performed before the migration task starts. The migration task only starts after the precheck succeeds.

   • If the precheck fails, click the icon next to each failed check item to view the related details. Fix the issues as instructed and run the precheck again.

9. Click Next.

10. In the Confirm Settings dialog box, configure the Channel Specification parameter. Then, read and select Data Transmission Service (Pay-as-you-go) Service Terms.

11. Click Buy and Start to start the data migration task.

Stop the data migration task

• Full data migration

  Do not manually stop a task during full data migration. Otherwise, the system may fail to migrate all data. Wait until the migration task automatically ends.

• Incremental data migration

  The task does not automatically end during incremental data migration. You must manually stop the migration task.

  1. Wait until the task progress bar shows Incremental Data Migration and The migration task is not delayed. Then, stop writing data to the source database for a few minutes. In some cases, the progress bar shows the delay time of incremental data migration.
  2. After the status of incremental data migration changes to The migration task is not delayed, manually stop the migration task.

What to do next

The database accounts that are used for data migration have the read and write permissions. After you migrate data, you must delete the database accounts to ensure security.

FAQ

• Q: What do I do if a migration task fails to pass the precheck?

  A: For more information, see Source database connectivity.

• Q: How do I troubleshoot a failed data migration task?

  A: For more information, see Fix a failed data migration task.