Migrate data from an RDS for MySQL instance to a Tablestore instance - Data Transmission Service

Data Transmission Service (DTS) lets you migrate data from an RDS for MySQL instance to a Tablestore instance.

Prerequisites

A destination Tablestore instance has been created.
Obtain the AccessKey ID and AccessKey secret of the Alibaba Cloud account that owns the Tablestore instance. For more information, see Create an AccessKey pair for an Alibaba Cloud account.

Precautions

Category	Description
Source database limits	The tables to be synchronized must have primary keys or UNIQUE constraints, and the fields must be unique. Otherwise, the destination database may contain duplicate data. If you select tables as the migration objects and need to edit them, such as mapping column names, a single synchronization task supports up to 1,000 tables. If you exceed this limit, a request error is reported after you submit the task. In this case, split the tables into multiple tasks or configure a task to synchronize the entire database. If you want to migrate incremental data, the following requirements for binary logs must be met: The binary logging feature is enabled. The binlog_format parameter is set to row and the binlog_row_image parameter is set to full. Otherwise, error messages are returned during the precheck and the data migration task fails to be started. Important If the source database is a self-managed MySQL database deployed in a dual-primary cluster, you must set the log_slave_updates parameter to ON. This ensures that DTS can obtain all binary logs. The binary logs of an ApsaraDB RDS for MySQL instance must be stored for at least three days. We recommend that you store the binary logs seven days. The binary logs of a self-managed MySQL database must be stored for at least seven days. Otherwise, DTS may fail to obtain the binary logs and the task may fail. In exceptional circumstances, data inconsistency or loss may occur. Make sure that you configure the retention period of binary logs based on the preceding requirements. Otherwise, the service reliability or performance stated in the Service Level Agreement (SLA) of DTS may not be guaranteed. Note For more information about how to set Retention Period of the binary logs of an ApsaraDB RDS for MySQL instance, see Configure parameters based on which the system automatically deletes the binary log files of an RDS instance. During schema migration and full data migration, do not perform DDL operations to change the schemas of databases or tables. Otherwise, the data migration task fails. Note During full data migration, DTS queries the source database. This creates metadata locks, which may block DDL operations on the source database. If you perform only full data migration, do not write new data to the source database. Otherwise, data inconsistency occurs between the source and destination databases. To maintain real-time data consistency, select schema migration, full data migration, and incremental data migration. In incremental data migration, an ApsaraDB RDS for MySQL instance that does not record transaction logs, such as a read-only ApsaraDB RDS for MySQL V5.6 instance, cannot be used as the source database. The data generated by change operation of binary logs, such as data restored from a physical backup or data from a cascade operation, is not recorded and migrated to the destination database when the data migration instance is running. Note If the change data is not recorded and migrated to the destination database, you can migrate full data again on the premise that your business is not affected. If the source database is MySQL database 8.0.23 or later, and the data to be migrated includes invisible columns, the data of the columns cannot be obtained and data loss occurs. Note To make the columns visible, run the `ALTER TABLE <table_name> ALTER COLUMN <column_name> SET VISIBLE;` command. For more information, see Invisible Columns. Tables that do not have primary keys automatically generate invisible primary keys. You need to make the invisible primary keys visible. For more information, see Generated Invisible Primary Keys.
Other limits	Do not use tools such as pt-online-schema-change to perform online DDL operations on migration objects in the source database. Otherwise, the migration fails. For columns of the FLOAT or DOUBLE data type, DTS reads the values using `ROUND(COLUMN,PRECISION)`. If you do not define a precision, DTS uses a default precision of 38 for FLOAT and 308 for DOUBLE. Confirm that this precision meets your business requirements. Before you migrate data, evaluate the performance of the source and destination databases. We recommend that you migrate data during off-peak hours. During full data migration, DTS consumes read and write resources on both the source and destination databases, which may increase database loads. Full data migration involves concurrent INSERT operations, which cause table fragmentation in the destination database. After full data migration is complete, the table storage space in the destination database is larger than that in the source instance. DTS attempts to resume tasks that failed within the last seven days. Before you switch your business to the destination instance, stop or release the DTS instance. You can also run the `REVOKE` command 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 would cause data in the source to overwrite data in the destination. The number of tables to be migrated must not exceed the limit of the Tablestore instance, which is 64 tables. If your business requires more tables, remove this limit for the destination Tablestore instance. The names of the tables or columns to be synchronized must follow the Tablestore naming conventions: The name of a table or column can contain letters, digits, and underscores (_). The name must start with a letter or an underscore (_). The name of a table or column must be 1 to 255 characters in length. If the source database is an ApsaraDB RDS for MySQL instance for which the EncDB feature is enabled, full data migration cannot be performed. Note ApsaraDB RDS for MySQL instances that have the Transparent Data Encryption (TDE) feature enabled support schema migration, full data migration, and incremental data migration. If an instance fails, DTS helpdesk will try to recover the instance within 8 hours. During the recovery process, operations such as restarting the instance and adjusting parameters may be performed. Note When parameters are adjusted, only the parameters of the DTS instance are modified. The parameters of the database are not modified. The parameters that may be modified include but are not limited to those described in Modify instance parameters.
Special cases	If the source database is a self-managed MySQL database, take note of the following limits: If you perform a primary/secondary switchover on the source database when the data migration task is running, the task fails. DTS calculates migration latency based on the timestamp of the latest migrated data in the destination database and the current timestamp in the source database. If no DML operation is performed on the source database for a long time, the migration latency may be inaccurate. If the latency of the data migration task is excessively high, you can perform a DML operation on the source database to update the latency. Note If you select an entire database as the object to be migrated, you can create a heartbeat table. The heartbeat table is updated or receives data every second. DTS executes the CREATE DATABASE IF NOT EXISTS `test` statement in the source database as scheduled to move forward the binary log file position. If the source database is an Apsara RDS for MySQL instance, take note of the following limit: In incremental data migration, an ApsaraDB RDS for MySQL instance that does not record transaction logs, such as a read-only ApsaraDB RDS for MySQL V5.6 instance, cannot be used as the source database. DTS executes the CREATE DATABASE IF NOT EXISTS `test` statement in the source database as scheduled to move forward the binary log file position.

Billing

Migration type	Task configuration fee	Data transfer cost
Schema migration and full data migration	Free of charge.	You are charged for data transfer if you migrate data from Alibaba Cloud over the Internet. For more information, see Billing overview.
Incremental data migration	Charged. For more information, see Billing overview.

Migration types

Schema migration
DTS migrates the schema definitions of the migration objects from the source database to the destination database.
Full migration
DTS migrates all historical data of the migration objects from the source database to the destination database.
Incremental migration
After full migration, DTS synchronizes incremental data updates from the source database to the destination database. Incremental data migration lets you smoothly migrate data without stopping your applications.

SQL operations supported for incremental migration

Operation type	SQL statement
DML	INSERT, UPDATE, DELETE

Permissions required for database accounts

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

For information about how to create a database account and grant permissions for an RDS for MySQL instance, see Create an account and Modify account permissions.

Procedure

Use one of the following methods to go to the Data Migration page and select the region in which the data migration instance resides.
DTS console
1. Log on to the DTS console.
2. In the left-side navigation pane, click Data Migration.
3. In the upper-left corner of the page, select the region in which the data migration instance resides.
DMS console
Note
The actual operation may vary based on the mode and layout of the DMS console. For more information, see Simple mode and Customize the layout and style of the DMS console.
1. Log on to the DMS console.
2. In the top navigation bar, move the pointer over Data + AI > DTS (DTS) > Data Migration.
3. From the drop-down list to the right of Data Migration Tasks, select the region in which the data synchronization instance resides.
Click Create Task to go to the task configuration page.

Configure the source and destination databases. The following table describes the parameters.

Category	Configuration	Description
None	Task Name	DTS automatically generates a task name. We recommend that you specify a descriptive name for easy identification. The name does not have to be unique.
Source Database	Select Existing Connection	If you use a database instance that is registered with DTS, select the instance from the drop-down list. DTS automatically populates the following database parameters for the instance. For more information, see Manage database connections. Note In the DMS console, you can select the database instance from the Select a DMS database instance drop-down list. If you fail to register the instance with DTS, or you do not need to use the instance that is registered with DTS, you must configure the following database information.
	Database Type	Select MySQL.
	Access Method	Select Cloud Instance.
	Instance Region	Select the region where the source RDS for MySQL instance resides.
	Replicate Data Across Alibaba Cloud Accounts	In this example, data is migrated within the same Alibaba Cloud account. Select No.
	RDS Instance ID	Select the ID of the source RDS for MySQL instance.
	Database Account	Enter the database account of the source RDS for MySQL instance. For information about the required permissions, see Permissions required for database accounts.
	Database Password	The password that is used to access the database instance.
	Encryption	Specifies whether to encrypt the connection to the source database instance. Select Non-encrypted or SSL-encrypted based on your business requirements. If you want to set this parameter to SSL-encrypted, you must enable SSL encryption for the ApsaraDB RDS for MySQL instance before you configure the DTS task. For more information, see Use a cloud certificate to enable SSL encryption.
Destination Database	Select Existing Connection	If you use a database instance that is registered with DTS, select the instance from the drop-down list. DTS automatically populates the following database parameters for the instance. For more information, see Manage database connections. Note In the DMS console, you can select the database instance from the Select a DMS database instance drop-down list. If you fail to register the instance with DTS, or you do not need to use the instance that is registered with DTS, you must configure the following database information.
	Database Type	Select Tablestore.
	Access Method	Select Cloud Instance.
	Instance Region	Select the region where the destination Tablestore instance resides.
	Instance ID	Select the name of the destination Tablestore instance.
	AccessKey ID Of Alibaba Cloud Account	Enter the AccessKey ID used to identify the user. For more information, see Create an AccessKey pair.
	AccessKey Secret Of Alibaba Cloud Account	Enter the AccessKey secret used to authenticate the user. For more information, see Create an AccessKey pair.

In the lower part of the page, click Test Connectivity and Proceed.
Note
- Make sure that the CIDR blocks of DTS servers can be 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 and its Access Method is not set to Alibaba Cloud Instance, click Test Connectivity in the CIDR Blocks of DTS Servers dialog box.

Configure the objects to be migrated.

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

Configuration	Description
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 you do not select Schema Migration, make sure a database and a table are created in the destination database to receive data and the object name mapping feature is enabled in Selected Objects. If you do not select Incremental Data Migration, we recommend that you do not write data to the source database during data migration. This ensures data consistency between the source and destination databases.
Processing Mode of Conflicting Tables	Precheck and Report Errors: checks whether the destination database contains tables that use the same names as tables in the source database. If the source and destination databases do not contain tables that have identical table names, the precheck is passed. Otherwise, an error is returned during the precheck and the data migration task cannot be started. Note If the source and destination databases contain tables with identical names and the tables in the destination database cannot be deleted or renamed, you can use the object name mapping feature to rename the tables that are migrated to the destination database. For more information, see Map object names. Ignore Errors and Proceed: skips the precheck for identical table names in the source and destination databases. Warning If you select Ignore Errors and Proceed, data inconsistency may occur and your business may be exposed to the following potential risks: If the source and destination databases have the same schema, and a data record has the same primary key as an existing data record in the destination database, the following scenarios may occur: During full data migration, DTS does not migrate the data record to the destination database. The existing data record in the destination database is retained. During incremental data migration, DTS migrates the data record to the destination database. The existing data record in the destination database is overwritten. If the source and destination databases have different schemas, only specific columns are migrated or the data migration task fails. Proceed with caution.
Synchronization Operation Types	Select the required operation types to synchronize. By default, all operation types are selected.
Dirty Data Handling Policy	Select the policy for handling data write errors. Valid values: Skip Block
Data Write Mode	Select the data write mode. Valid values: Update Row: The PutRowChange operation is used to perform row-level updates. Overwrite Row: The UpdateRowChange operation is used to perform row-level overwrites.
Batch Write Mode	The API operation that is called for batch writes. Valid values: BulkImportRequest: Offline write. BatchWriteRowRequest: Batch write. We recommend that you select BulkImportRequest for higher read and write efficiency and to reduce billing costs for the Tablestore instance.
More Settings	You can configure the following parameters as needed: Queue Size: The queue length of the data writing process for the Tablestore instance. Thread Count: The number of callback processing threads for the data writing process of the Tablestore instance. Concurrency: The concurrent request limit for the Tablestore instance. Bucket Count: The number of concurrent buckets for sequential writing of incremental data. A larger value improves concurrent write capabilities. Note This value must be less than or equal to the value of Concurrency.
Case Sensitivity For Destination Object Names	The capitalization of database names, table names, and column names in the destination instance. By default, DTS default policy is selected. You can select other options to make sure that the capitalization of object names is consistent with that of the source or destination database. For more information, see Specify the capitalization of object names in the destination instance.
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 The migration granularity is at the database and table level. If you select only tables as migration objects, other objects, such as views, triggers, and stored procedures, are not migrated. You can synchronize tables only from a single database. You can select one database or multiple tables from the same database.
Selected Objects	To rename an object that you want to migrate to the destination instance, right-click the object in the Selected Objects section. For more information, see Map the name of a single object. To rename multiple objects at a time, click Batch Edit in the upper-right corner of the Selected Objects section. For more information, see Map multiple object names at a time. Note Hover the mouse pointer over a table to synchronize and click the Edit icon that appears. Then, you can set the data type for each column of the table in the Tablestore instance. Only table names support mapping. If you use the object name mapping feature, the migration of other objects that depend on the mapped object may fail. To set a WHERE clause to filter data, right-click the table to be migrated in the Selected Objects box and set the filter condition in the dialog box that appears. For more information, see Set filter conditions.

Click Next: Advanced Settings to configure advanced settings.

Configuration	Description
Dedicated Cluster for Task Scheduling	By default, DTS schedules the data migration task to the shared cluster if you do not specify a dedicated cluster. If you want to improve the stability of data migration tasks, purchase a dedicated cluster. For more information, see What is a DTS dedicated cluster.
Retry Time for Failed Connections	The retry time range for failed connections. If the source or destination database fails to be connected after the data migration task is started, DTS immediately retries a connection within the retry time range. Valid values: 10 to 1,440. Unit: minutes. Default value: 720. We recommend that you set the parameter to a value greater than 30. If DTS is reconnected to the source and destination databases within the specified retry time range, DTS resumes the data migration task. Otherwise, the data migration task fails. Note If you specify different retry time ranges for multiple data migration tasks that share the same source or destination database, the value that is specified later takes precedence. When DTS retries a connection, you are charged for the DTS instance. We recommend that you specify the retry time range based on your business requirements. You can also release the DTS instance at the earliest opportunity after the source database and destination instance are released.
Retry Time for Other Issues	The retry time range for other issues. For example, if DDL or DML operations fail to be performed after the data migration task is started, DTS immediately retries the operations within the retry time range. Valid values: 1 to 1440. Unit: minutes. Default value: 10. We recommend that you set the parameter to a value greater than 10. If the failed operations are successfully performed within the specified retry time range, DTS resumes the data migration task. Otherwise, the data migration task fails. Important The value of the Retry Time for Other Issues parameter must be smaller than the value of the Retry Time for Failed Connections parameter.
Enable Throttling for Full Data Migration	Specifies whether to enable throttling for full data migration. During full data migration, DTS uses the read and write resources of the source and destination databases. This may increase the loads of the database servers. You can enable throttling for full data migration based on your business requirements. To configure throttling, you must configure the Queries per second (QPS) to the source database, RPS of Full Data Migration, and Data migration speed for full migration (MB/s) parameters. This reduces the loads of the destination database server. Note You can configure this parameter only if you select Full Data Migration for the Migration Types parameter.
Enable Throttling for Incremental Data Migration	Specifies whether to enable throttling for incremental data migration. To configure throttling, you must configure the RPS of Incremental Data Migration and Data migration speed for incremental migration (MB/s) parameters. This reduces the loads of the destination database server. Note You can configure this parameter only if you select Incremental Data Migration for the Migration Types parameter.
Environment Tag	You can select an environment tag to identify the instance. In this example, no selection is required.
Whether to delete SQL operations on heartbeat tables of forward and reverse tasks	Specifies whether to write SQL operations on heartbeat tables to the source database while the DTS instance is running. Valid values: Yes: does not write SQL operations on heartbeat tables. In this case, a latency of the DTS instance may be displayed. No: writes SQL operations on heartbeat tables. In this case, features such as physical backup and cloning of the source database may be affected.
Configure ETL	Specifies whether to enable the extract, transform, and load (ETL) feature. For more information, see What is ETL? Valid values: Yes: configures the ETL feature. You can enter data processing statements in the code editor. For more information, see Configure ETL in a data migration or data synchronization task. No: does not configure the ETL feature.
Monitoring and Alerting	Specifies whether to configure alerting for the data migration task. If the task fails or the migration latency exceeds the specified threshold, the alert contacts receive notifications. Valid values: No: does not configure alerting. Yes: configures alerting. In this case, you must also configure the alert threshold and alert notification settings. For more information, see the Configure monitoring and alerting when you create a DTS task section of the Configure monitoring and alerting topic.

After you complete the configurations, click Next: Configure Database And Table Fields to configure the primary key columns for the tables to be synchronized in the Tablestore instance.

Save the task settings and run a precheck.
- To view the parameters to be specified when you call the relevant API operation to configure the DTS task, move the pointer over Next: Save Task Settings and Precheck and click Preview OpenAPI parameters.
- If you do not need to view or have viewed the parameters, click Next: Save Task Settings and Precheck in the lower part of the page.
Note
- Before you can start the data migration task, DTS performs a precheck. You can start the data migration task only after the task passes the precheck.
- If the task fails to pass the precheck, click View Details next to each failed item. After you analyze the causes based on the check results, troubleshoot the issues. Then, run a precheck again.
- If an alert is triggered for an item during the precheck:
  If an alert item cannot be ignored, click View Details next to the failed item and troubleshoot the issues. Then, run a precheck again.
  If the alert item can be ignored, click Confirm Alert Details. In the View Details dialog box, click Ignore. In the message that appears, click OK. Then, click Precheck Again to run a precheck again. If you ignore the alert item, data inconsistency may occur, and your business may be exposed to potential risks.

Purchase the instance.

Wait until Success Rate becomes 100%. Then, click Next: Purchase Instance.

On the Purchase Instance page, configure the Instance Class parameter for the data migration instance. The following table describes the parameters.

Section	Parameter	Description
New Instance Class	Resource Group	The resource group to which the data migration instance belongs. Default value: default resource group. For more information, see What is Resource Management?
New Instance Class	Instance Class	DTS provides instance classes that vary in the migration speed. You can select an instance class based on your business scenario. For more information, see Instance classes of data migration instances.

Read and agree to Data Transmission Service (Pay-as-you-go) Service Terms by selecting the check box.
Click Buy and Start. In the message that appears, click OK.
You can view the progress of the task on the Data Migration page.
Note
- If a data migration task cannot be used to migrate incremental data, the task automatically stops. The Completed is displayed in the Status section.
- If a data migration task can be used to migrate incremental data, the task does not automatically stop. The incremental data migration task never stops or completes. The Running is displayed in the Status section.