Migrate RDS MySQL to MaxCompute - Data Transmission Service

Prerequisites

Create a destination MaxCompute project with more storage space than is used by the source ApsaraDB RDS for MySQL instance. For more information, see Create a MaxCompute project.
Configure an IP address whitelist for MaxCompute to allow access from DTS. For more information, see Configure an IP address whitelist to allow Alibaba Cloud services to access MaxCompute.
Use an Alibaba Cloud account (primary account) to create and record an AccessKey pair.

Note
Alternatively, create a RAM user and record its AccessKey pair, and then assign the user a super administrator role (admin or super_administrator).

Limitations

Note

DTS does not migrate foreign keys. As a result, cascade operations such as cascade delete in the source database are not replicated in the destination database.

Type	Description
Source database limitations	Migrated tables must have a primary key or a unique constraint, and the values in the columns of the key or constraint must be unique. Otherwise, the destination database may contain duplicate data. If you perform table-level migration with editing operations like column name mapping, a single migration task supports up to 1,000 tables. Submitting a task with more tables causes an error. We recommend that you either split the tables into multiple migration tasks or configure a single task to migrate the entire database. If you need incremental migration, enable binary logging: Set binlog_format to ROW and binlog_row_image to FULL. Otherwise, the precheck fails and the task cannot start. Important If your self-managed MySQL source is a dual-master cluster—where each instance acts as both master and slave—enable the log_slave_updates parameter. This ensures DTS can read all binary logs. For RDS for MySQL instances, retain local binary logs for at least three days (seven days recommended). For self-managed MySQL databases, retain local binary logs for at least seven days. If DTS cannot access binary logs, the task fails. In extreme cases, data inconsistency or data loss may occur. Issues caused by binary log retention periods shorter than DTS requires are not covered under the DTS SLA. Note To set the retention period for local binary logs on an RDS for MySQL instance, see Automatically delete local logs. During the schema migration and full migration phases, do not perform DDL operations that change the database or table schema. Otherwise, the data migration task will fail. Note During the full migration phase, DTS queries the source database. This creates a metadata lock, which may block DDL operations on the source database. If you perform only a full data migration, do not write new data to the source database. Otherwise, data inconsistency will occur between the source and destination databases. To maintain real-time data consistency, select schema migration, full data migration, and incremental data migration. If you need incremental migration, RDS for MySQL instances that do not record transaction logs—such as RDS for MySQL 5.6 read-only instances—are not supported as sources. DTS does not migrate data generated by changes that do not write to binary logs. Examples include data restored from physical backups or created by cascade operations. Note If this occurs, re-run full migration after your business allows it. If your source MySQL database is version 8.0.23 or later and contains invisible hidden columns, DTS cannot read those columns. This may cause data loss. Note Run `ALTER TABLE <table_name> ALTER COLUMN <column_name> SET VISIBLE;` to make the hidden column visible. For more information, see Invisible Columns.
Other limitations	DTS does not support migrating the following object types: INDEX, PARTITION, VIEW, PROCEDURE, FUNCTION, TRIGGER, and foreign keys (FK). Because MaxCompute does not support primary key constraints, if DTS re-transmits data due to network issues or other reasons, duplicate records may appear in MaxCompute. Do not use tools like pt-online-schema-change to perform online DDL changes on the migration objects in the source database. Otherwise, the migration task fails. For columns of the FLOAT or DOUBLE data type, DTS reads the values by using the `ROUND(COLUMN,PRECISION)` function. If you do not specify the precision, DTS uses a default precision of 38 digits for FLOAT and 308 digits for DOUBLE. Make sure that the migration precision meets your business requirements. Before you perform data migration, evaluate the performance of the source and destination databases. We recommend that you perform data migration during off-peak hours because full data migration consumes read and write resources of both databases and may increase the workload. Full data migration involves concurrent INSERT operations, which cause table fragmentation in the destination database. After full data migration, tables in the destination database will use more storage space than in the source instance. DTS attempts to resume tasks for failed migration instances within seven days. Therefore, before you switch your workloads to the destination instance, you must stop or release the DTS instance, or use the `REVOKE` statement to revoke the write permissions from the account that DTS uses to access the destination instance. This prevents the task from being automatically resumed, which could cause the source data to overwrite data in the destination instance. If your RDS for MySQL instance has Always-Encrypted enabled, full migration is not supported. Note RDS for MySQL instances with Transparent Data Encryption (TDE) enabled support schema migration, full migration, and incremental migration. If a task fails, DTS support staff will attempt to restore it within eight hours. During restoration, they may restart the task or adjust its parameters. Note Only DTS task parameters are modified—not database parameters. Parameters that may be adjusted include those listed in Modify instance parameters.
Special cases	For self-managed MySQL sources: A master–standby switchover on the source database causes the migration task to fail. DTS calculates latency by comparing the timestamp of the last record migrated to the destination database with the current time. If no DML operations run on the source for a long time, latency reporting becomes inaccurate. If latency appears too high, run a DML operation on the source to update the latency value. Note If you select full-database migration, create a heartbeat table. Update or write to it every second. DTS periodically runs CREATE DATABASE IF NOT EXISTS `test` on the source database to advance the binary log offset. If your source is Amazon Aurora MySQL or another clustered MySQL instance, ensure the domain name or IP address configured for the task—and its DNS resolution—always points to a read–write (RW) node. Otherwise, the migration task may fail. For RDS for MySQL sources: If you need incremental migration, RDS for MySQL instances that do not record transaction logs—such as RDS for MySQL 5.6 read-only instances—are not supported as sources. DTS periodically runs CREATE DATABASE IF NOT EXISTS `test` on the source database to advance the binary log offset.

Billing

Migration type	Task configuration fee	Internet traffic fee
Schema migration and full data migration	No charge.	No charge in this example. Note Setting the destination database's Access Method to Public IP Address incurs internet traffic fees. For more information, see Billing overview.
Incremental data migration	Charged. For more information, see Billing overview.

Migration types

Schema migration

DTS migrates the schemas of the source tables to MaxCompute and appends the _base suffix to the table names during initialization. For example, if a source table is named customer, the corresponding table in MaxCompute is named customer_base.
Full data migration

DTS migrates all historical data from the source tables to the _base tables in MaxCompute. This data becomes the baseline for the subsequent incremental data migration. For example, data from the customer table in the source database is migrated to the customer_base table in MaxCompute.

Note
This table is also called the full baseline table.
Incremental data migration

DTS creates an incremental log table in MaxCompute and migrates incremental data from the source database to this table in real time. The table is named by appending the _log suffix to the source table name, for example, customer_log.

Note
For more information about the schema of the incremental log table, see Incremental log table schema.

SQL operations for incremental migration

Type	SQL statement
DML	INSERT, UPDATE, DELETE
DDL	ADD COLUMN Note ADD COLUMN operations with attributes are not supported.

Database account permissions

Database	Schema migration	Full data migration	Incremental data migration
RDS MySQL	SELECT permission	SELECT permission	REPLICATION SLAVE, REPLICATION CLIENT, and the SELECT permission on the objects to be migrated. DTS automatically grants these permissions.
MaxCompute	Read and write permissions

To create an RDS MySQL database account and grant permissions, see Create an account and Modify account permissions.

Procedure

Navigate to the migration task list page for the destination region using one of the following methods.
From the DTS console
1. Log on to the Data Transmission Service (DTS) console.
2. In the navigation pane on the left, click Data Migration.
3. In the upper-left corner of the page, select the region where the migration instance is located.
From the DMS console

Note
The actual operations may vary based on the mode and layout of the DMS console. For more information, see Simple mode console and Customize the layout and style of the DMS console.
1. Log on to the Data Management (DMS) console.
2. In the top menu bar, choose Data + AI > Data Transmission (DTS) > Data Migration.
3. To the right of Data Migration Tasks, select the region where the migration instance is located.
Click Create Task to navigate to the task configuration page.

Configure the source and destination databases.

Category	Parameter	Description
N/A	Task Name	DTS automatically generates a task name. Use a descriptive name for easy identification. The name does not need to be unique.
Source Database	Select Existing Connection	To use a database instance that has been added to the system (created or saved), select the desired database instance from the drop-down list. The database information below will be automatically configured. Note In the DMS console, this parameter is named Select a DMS database instance.. If you have not registered the database instance with the system, or do not need to use a registered instance, manually configure the database information below.
	Database Type	Select MySQL.
	Access Method	Select Alibaba Cloud Instance.
	Instance Region	Select the region of the source RDS MySQL instance.
	Replicate Data Across Alibaba Cloud Accounts	In this example, a database instance under the current Alibaba Cloud account is used. Select No.
	RDS Instance ID	Select the instance ID of the source RDS MySQL instance.
	Database Account	Enter the database account of the source RDS MySQL instance. For information about the required permissions, see Permissions required for database accounts.
	Database Password	Enter the password for the database account.
	Connection Method	Select Non-encrypted or SSL-encrypted based on your database requirements. If you set this parameter to SSL-encrypted, you must enable SSL encryption for the RDS for MySQL instance beforehand. For more information, see Quickly enable SSL encryption using a cloud certificate.
Destination Database	Select Existing Connection	To use a database instance that has been added to the system (created or saved), select the desired database instance from the drop-down list. The database information below will be automatically configured. Note In the DMS console, this parameter is named Select a DMS database instance.. If you have not registered the database instance with the system, or do not need to use a registered instance, manually configure the database information below.
	Database Type	Select MaxCompute.
	Access Method	Select Alibaba Cloud Instance.
	Instance Region	Select the region of the target MaxCompute project.
	Project	Enter the name of the target MaxCompute project.
	AccessKey ID of Alibaba Cloud Account	Enter the AccessKey pair that you prepared in Prerequisites.
	AccessKey Secret of Alibaba Cloud Account

After you complete the configuration, click Test Connectivity and Proceed at the bottom of the page.
Note
- Ensure that the IP address segment of the DTS service is automatically or manually added to the security settings of the source and destination databases to allow access from DTS servers. For more information, see Add DTS server IP addresses to a whitelist.
- If the source or destination database is a self-managed database (the Access Method is not Alibaba Cloud Instance), you must also click Test Connectivity in the CIDR Blocks of DTS Servers dialog box that appears.
Click OK to authorize the MaxCompute account.

Configure the task objects.

On the Configure Objects page, configure the objects that you want to migrate.

Parameter	Description
Migration Types	If you only need to perform a full migration, select both Schema Migration and Full Data Migration. To perform a migration with no downtime, select Schema Migration, Full Data Migration, and Incremental Data Migration. Note If you do not select Schema Migration, you must ensure that a database and tables to receive the data exist in the destination database. You can also use the object name mapping feature in the Selected Objects box as needed. If you do not select Incremental Data Migration, do not write new data to the source instance during data migration to ensure data consistency.
Naming Rules of Additional Columns	When DTS migrates data to MaxCompute, it adds additional columns to the target tables. Select New Rule or Previous Rule based on your business requirements. Warning Before you select a rule, check whether the names of the additional columns conflict with existing column names in the target tables. Name conflicts can cause the data migration to fail or lead to data loss. For more information about the rules and definitions of the additional columns, see Names and definitions of additional columns.
Partition Definition of Incremental Data Table	Select a partition name based on your business requirements. For more information about partitions, see Partition.
Processing Mode of Conflicting Tables	Precheck and Report Errors: Checks whether tables with the same names exist in the destination database. If no tables with the same names exist, the precheck is passed. If tables with the same names exist, an error is reported during the precheck, and the data migration task does not start. Note If a table in the destination database has the same name but cannot be easily deleted or renamed, you can change the name of the table in the destination database. For more information, see Object name mapping. Ignore Errors and Proceed: Skips the check for tables with the same names. Warning Selecting Ignore Errors and Proceed may cause data inconsistency and business risks. For example: If the table schemas are consistent and a record in the destination database has the same primary key value as a record in the source database: During full migration, DTS keeps the record in the destination database. The record from the source database is not migrated. During incremental migration, DTS does not keep the record in the destination database. The record from the source database overwrites the record in the destination database. If the table schemas are inconsistent, only some columns of data may be migrated, or the migration may fail. Proceed with caution.
Capitalization of Object Names in Destination Instance	You can configure the case sensitivity policy for the names of migrated objects, such as databases, tables, and columns, in the destination instance. By default, DTS default policy is selected. You can also choose to keep the case sensitivity consistent with the default policy of the source or destination database. For more information, see Case sensitivity of object names in the destination database.
Source Objects	Select one or more objects from the Source Objects section. Click the icon and add the objects to the Selected Objects section. Note You can select objects only at the table level.
Selected Objects	To change the name of a single migration object in the target instance, right-click the object in the Selected Objects box. For more information, see Map individual schema, table, and column names. To change the names of multiple migration objects in the target instance, click Selected Objects in the upper-right corner of the Batch Edit box. For more information, see Map multiple schema, table, and column names. Note If you use the object name mapping feature, the migration of other objects that depend on the renamed object may fail. To filter data by using a WHERE clause, right-click the table to be migrated in the Selected Objects box and specify the filter conditions in the dialog box that appears. For instructions, see Configure filter conditions. To select SQL operations to be migrated at the database or table level, right-click the object in the Selected Objects box and select the desired SQL operations in the dialog box that appears.

Click Next: Advanced Settings to configure advanced parameters.

Parameter	Description
Dedicated Cluster for Task Scheduling	By default, DTS schedules tasks on a shared cluster. You do not need to select one. If you want more stable tasks, you can purchase a dedicated cluster to run DTS migration tasks.
Retry Time for Failed Connections	After the migration task starts, if the connection to the source or destination database fails, DTS reports an error and immediately begins to retry the connection. The default retry duration is 720 minutes. You can customize the retry time to a value from 10 to 1440 minutes. We recommend that you set the duration to more than 30 minutes. If DTS reconnects to the source and destination databases within the specified duration, the migration task automatically resumes. Otherwise, the task fails. Note For multiple DTS instances that share the same source or destination, the network retry time is determined by the setting of the last created task. Because you are charged for the task during the connection retry period, we recommend that you customize the retry time based on your business needs, or release the DTS instance as soon as possible after the source and destination database instances are released.
Retry Time for Other Issues	After the migration task starts, if a non-connectivity issue, such as a DDL or DML execution exception, occurs in the source or destination database, DTS reports an error and immediately begins to retry the operation. The default retry duration is 10 minutes. You can customize the retry time to a value from 1 to 1440 minutes. We recommend that you set the duration to more than 10 minutes. If the related operations succeed within the specified retry duration, the migration task automatically resumes. Otherwise, the task fails. Important The value of Retry Time for Other Issues must be less than the value of Retry Time for Failed Connections.
Enable Throttling for Full Data Migration	During full migration, DTS consumes read and write resources on the source and destination databases, which may increase the database load. If required, you can enable throttling for the full migration task. You can set Queries per second (QPS) to the source database, RPS of Full Data Migration, and Data migration speed for full migration (MB/s) to reduce the load on the destination database. Note This configuration item is available only if you select Full Data Migration for Migration Types. You can also adjust the full migration speed after the migration instance is running.
Enable Throttling for Incremental Data Migration	If required, you can also choose to set speed limits for the incremental migration task. You can set RPS of Incremental Data Migration and Data migration speed for incremental migration (MB/s) to reduce the load on the destination database. Note This configuration item is available only if you select Incremental Data Migration for Migration Types. You can also adjust the incremental migration speed after the migration instance is running.
Whether to delete SQL operations on heartbeat tables of forward and reverse tasks	Choose whether DTS writes heartbeat SQL information to the source database while the instance is running. Yes: Does not write heartbeat SQL information to the source database. The DTS instance may display latency. No: Writes heartbeat SQL information to the source database. This may interfere with source database operations like physical backups and cloning.
Environment Tag	Select an environment tag to identify the instance. This parameter is optional.
Configure ETL	Choose whether to enable the extract, transform, and load (ETL) feature. For more information, see What is ETL? Valid values: Yes: Enables the ETL feature. Enter data processing statements in the code editor. For more information, see Configure ETL in a data migration or data synchronization task. No: Disables the ETL feature.
Monitoring and Alerting	Select whether to set alerts and receive alert notifications based on your business needs. No: Does not set an alert. Yes: Configure alerts by setting an alert threshold and an alert notifications. If a migration fails or the latency exceeds the threshold, the system sends an alert notification.

Save the task and run a precheck.
- To view the parameters for configuring this instance when you call the API operation, move the pointer over the Next: Save Task Settings and Precheck button and click Preview OpenAPI parameters in the bubble that appears.
- If you do not need to view or have finished viewing the API parameters, click Next: Save Task Settings and Precheck at the bottom of the page.
Note
- Before the migration task starts, DTS performs a precheck. The task starts only after it passes the precheck.
- If the precheck fails, click View Details next to the failed check item, fix the issue based on the prompt, and then run the precheck again.
- If a warning is reported during the precheck:
  
  For check items that cannot be ignored, click View Details next to the failed item, fix the issue based on the prompt, and then run the precheck again.
  
  For check items that can be ignored, you can click Confirm Alert Details, Ignore, OK, and Precheck Again to skip the alert item and run the precheck again. If you choose to ignore a warning, it may cause issues such as data inconsistency and pose risks to your business.

Purchase the instance.

When the Success Rate is 100%, click Next: Purchase Instance.

On the Purchase page, select the link specification for the data migration instance. For more information, see the following table.

Category	Parameter	Description
New Instance Class	Resource Group Settings	Select the resource group to which the instance belongs. The default value is default resource group. For more information, see What is Resource Management?
New Instance Class	Instance Class	DTS provides migration specifications with different performance levels. The link specification affects the migration speed. You can select a specification based on your business scenario. For more information, see Data migration link specifications.

After the configuration is complete, read and select Data Transmission Service (Pay-as-you-go) Service Terms.
Click Buy and Start. In the OK dialog box that appears, click OK.

You can view the progress of the migration task on the Data Migration Tasks list page.
Note
- If the migration task does not include incremental migration, it stops automatically after the full migration is complete. After the task stops, its Status changes to Completed.
- If the migration task includes incremental migration, it does not stop automatically. The incremental migration task continues to run. While the incremental migration task is running, the Status of the task is Running.

Incremental log table schema