Migrate data from an ApsaraDB RDS for MySQL instance to an ApsaraDB for SelectDB instance - Data Transmission Service

ApsaraDB for SelectDB can respond to queries on large amounts of data within sub-seconds, handle tens of thousands of concurrent point queries, and perform complex analysis with high throughput. Data Transmission Service (DTS) allows you to migrate data from a self-managed MySQL database or an ApsaraDB RDS for MySQL instance to an ApsaraDB for SelectDB instance. This helps you analyze large amounts of data. This topic describes how to migrate data from an ApsaraDB RDS for MySQL instance to an ApsaraDB for SelectDB instance by using DTS.

Prerequisites

The destination ApsaraDB for SelectDB instance is created. The available storage space of this instance is larger than the total size of data in the source ApsaraDB RDS for MySQL instance. For more information, see Create an instance.

Usage notes

Limit type	Description
Limits on the source database	The server on which the source database is deployed must have sufficient outbound bandwidth. Otherwise, the data migration speed decreases. Requirements for the objects to be migrated: The tables to be migrated have PRIMARY KEY or UNIQUE constraints: Make sure all fields must be unique. Otherwise, the destination database may contain duplicate data. The objects to be migrated contain tables that do not have primary keys or UNIQUE constraints: We recommend that you select Schema Migration for the Migration Types parameter and duplicate for the Engine parameter in the Configurations for Databases, Tables, and Columns step when you configure an instance. Note During schema migration, DTS automatically adds fields to destination tables. For more information, see the Additional columns section of this topic. If you select tables as the objects to be migrated and you want to modify the tables in the destination database, such as renaming tables or columns, you can migrate up to 1,000 tables in a single data migration task. If you run a task to migrate more than 1,000 tables, a request error occurs. In this case, we recommend that you configure multiple tasks to migrate the tables or configure a task to migrate 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 the source 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. Limits on operations to be performed on the source database: During schema migration and full data migration, do not execute DDL statements to change the schemas of databases or tables. Otherwise, the data migration task fails. If you perform only full data migration, do not write data to the source database during data migration. Otherwise, data inconsistency between the source and destination databases occurs. To ensure data consistency, we recommend that you select schema migration, full data migration, and incremental data migration as the migration types. If the data from the change operation in the binary logs is not recorded when a data migration instance is running, such as restore a data from a physical backup and data generated from cascade operation, the data cannot be migrated to destination database . Note If the change data is not migrated, you can migrate full data again on the premise that your business is not affected. If the source database is ApsaraDB RDS for MySQL database 8.0.23 or later and the data to be migrated contains invisible hidden columns, the data of the hidden columns fails to be obtained and data loss occurs Note You can run the `ALTER TABLE <table_name> ALTER COLUMN <column_name> SET VISIBLE;` command to set the hidden column as visible. For more information, see Invisible Columns. If the tables to be migrated do not contain a primary key, a hidden primary key is automatically generated. In this case, you can set the hidden primary key as visible. For more information, see Generated Invisible Primary Keys.
Other limits	You can migrate data to only tables that use the Unique Key model or Duplicate key model in ApsaraDB for SelectDB instances. If you migrate data to the destination table that uses the Duplicate key model, and if one of the following operations occurs, duplicate data may exist in the destination database. In this case, you can deduplicate the data based on additional columns such as _is_deleted, _version, and _record_id. Retry operation occured in a data migration instance. Retry operation was executed in a data migration instance. Two or more DML operations were executed for the same row of data after a data migration instance started. Note When the destination table is the table that uses the Duplicate key model, DTS converts UPDATE or DELETE statements to INSERT statements. You can specify only the `bucket_count` parameter in the Selected Objects section. Note The `bucket_count` parameter value must be a positive integer. Default value: auto. During data migration, do not create clusters in the destination ApsaraDB for SelectDB instance. Otherwise, the data migration task fails. You can restart the data migration instance to resume the data migration task that failed. ApsaraDB for SelectDB instances support only database names and table names that start with letters. If the name of a database or table that you want to migrate does not start with a letter, you must use the object name mapping feature to rename the database or table. If the name of the object that you want to migrate, such as a database, a table, or a column, contains Chinese characters, you must use the object name mapping feature to rename the object. For example, you can change the name from Chinese to English. Otherwise, the task may fail. During data migration, do not add backend nodes to the ApsaraDB for SelectDB database. Otherwise, the task fails. You can restart the data migration instance to resume the task that failed. In ApsaraDB RDS for MySQL, M of the `VARCHAR(M)` data type represents the character length. In ApsaraDB for SelectDB, N of the `VARCHAR(N)` data type represents the byte length. If you do not use the schema synchronization feature provided by DTS, we recommend that you set the length of a VARCHAR field in ApsaraDB for SelectDB to four times the length of a VARCHAR field in ApsaraDB RDS for MySQL. 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. During initial full data migration, DTS uses the read and write resources of the source and destination databases. This may increase the loads on the database servers. During initial full data synchronization, concurrent INSERT operations cause fragmentation in the tables of the destination database. After the initial full data synchronization is complete, the size of used tablespace of the destination database is larger than that of the source database. During data migration, do not use tools such as pt-online-schema-change to perform online DDL operations on the objects to be migrated from the source database. Otherwise, the data migration task fails. Data inconsistency between the source and destination databases may occur if data from other sources is written to the destination database during data migration. 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 a DTS task fails to run, DTS technical support will try to restore the task within 8 hours. During the restoration, the task may be restarted, and the parameters of the task may be modified. Note Only the parameters of the task may be modified. The parameters of databases are not modified. The parameters that may be modified include but are not limited to the parameters in the Modify instance parameters section of the "Modify the parameters of a DTS instance" topic.
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	Internet data transfer fee
Schema migration and full data migration	Free of charge.	Free of charge in this example.
Incremental data migration	Charged. For more information, see Billing overview.	Free of charge in this example.

SQL operations that support incremental migration

Operation type	SQL statement
DML	INSERT, UPDATE, and DELETE
DDL	ADD COLUMN DROP COLUMN and DROP TABLE TRUNCATE TABLE

Permissions required for database accounts

Database	Schema migration	Full data migration	Incremental data migration
Source ApsaraDB RDS for MySQL instance	The SELECT permission	The SELECT permission	Read and write permissions
Destination ApsaraDB for SelectDB instance	The USAGE_PRIV permission and the following read and write permissions: SELECT_PRIV, LOAD_PRIV, ALTER_PRIV, CREATE_PRIV, and DROP_PRIV

To create a database account and grant permissions to the database account, perform the following operations:

ApsaraDB RDS for MySQL instance: Create an account and Modify account permissions.
ApsaraDB for SelectDB instance: Manage the permissions to access clusters and Manage the basic permissions of users.

Note

If the source database account that you use is not created and granted permissions in the ApsaraDB RDS for MySQL console, make sure that the account has the REPLICATION CLIENT, REPLICATION SLAVE, SHOW VIEW, and SELECT 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.
Optional. Click New Configuration Page in the upper-right corner of the page.
Note
- Skip this step if the Back to Previous Version button is displayed in the upper-right corner of the page.
- Specific parameters in the new and previous versions of the configuration page may be different. We recommend that you use the new version of the configuration page.

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

Section	Parameter	Description
N/A	Task Name	The name of the DTS task. DTS automatically generates a task name. We recommend that you specify a descriptive name that makes it easy to identify the task. You do not need to specify a unique task name.
Source Database	Select Existing Connection	The instance that you want to use. You can choose whether to use an existing instance based on your business requirements. If you select an existing instance, DTS automatically populates the parameters for the database. If you do not use an existing instance, you must configure the database information below. Note You can register a database with DTS on the Database Connections page or the new configuration page. For more information, see Manage database connections. In the DMS console, you can select an existing database from the Select a DMS database instance. drop-down list. You can also click Add DMS Database Instance or go back to the homepage of the DMS console to register a database with DMS. For more information, see Register an Alibaba Cloud database instance and Register a database hosted on a third-party cloud service or a self-managed database.
	Database Type	The type of the source database. Select MySQL.
	Access Method	The access method of the source database. Select Alibaba Cloud Instance.
	Instance Region	The region in which the source ApsaraDB RDS for MySQL instance resides.
	Replicate Data Across Alibaba Cloud Accounts	Specifies whether to migrate data across Alibaba Cloud accounts. Select No.
	RDS Instance ID	Select the ID of the source ApsaraDB RDS for MySQL instance.
	Database Account	The database account of the source ApsaraDB RDS for MySQL instance. For 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 that is used to access the database.
	Encryption	Specifies whether to encrypt the connection to the database. You can 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	The instance that you want to use. You can choose whether to use an existing instance based on your business requirements. If you select an existing instance, DTS automatically populates the parameters for the database. If you do not use an existing instance, you must configure the database information below. Note You can register a database with DTS on the Database Connections page or the new configuration page. For more information, see Manage database connections. In the DMS console, you can select an existing database from the Select a DMS database instance. drop-down list. You can also click Add DMS Database Instance or go back to the homepage of the DMS console to register a database with DMS. For more information, see Register an Alibaba Cloud database instance and Register a database hosted on a third-party cloud service or a self-managed database.
	Database Type	The type of the destination database. Select SelectDB.
	Access Method	The access method of the destination database. Select Alibaba Cloud Instance.
	Instance Region	The region in which the destination ApsaraDB for SelectDB instance resides.
	Replicate Data Across Alibaba Cloud Accounts	Specifies whether to migrate data across Alibaba Cloud accounts. Select No.
	Instance ID	The ID of the destination ApsaraDB for SelectDB instance.
	Database Account	The database account of the destination ApsaraDB for SelectDB instance. For 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 that is used to access the database instance.

Click Test Connectivity and Proceed in the lower part of the page.
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 the CIDR blocks of DTS servers.
- 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.

Parameter	Description
Migration Types	To perform only full data migration, select both Schema Migration and Full Data Migration. To ensure service continuity during data migration, select Schema Migration, Full Data Migration, and Incremental Data Migration. Important After you migrate data from an ApsaraDB RDS for MySQL instance to an ApsaraDB for SelectDB instance, the data types are converted. If you do not select Schema Migration for the Migration Types parameter, you must create tables that use the Unique Key model or Duplicate key model in the destination ApsaraDB for SelectDB instance before data migration. The schemas of the destination tables must be compatible with the migrated data. For more information, see Data type mappings, Additional columns and Data models. 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.
Capitalization of Object Names in Destination Instance	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 to add the objects to the Selected Objects section. Note Select columns, tables, or databases as the objects to be migrated.
Selected Objects	To change a table name to be used in the destination project, right-click the table in the Selected Objects section. For more information, see Map object names. If you select Schema Migration for the Migration Types parameter, you can select only tables as the objects to be migrated and the `bucket_count` parameter must be set. Right-click a table to be migrated in the Selected Objects section, select Yes for the Enable Parameter Settings parameter in the Parameter Settings section that appears, specify Value based on your business requirements, and click OK. Note To select the SQL operations performed on a specific database or table, right-click the object in the Selected Objects section. In the dialog box that appears, select the SQL operations that you want to migrate. For more information, see the SQL operations that support incremental migration section of this topic. To specify WHERE conditions to filter data, right-click a table in the Selected Objects section. In the dialog box that appears, specify the conditions. For more information, see Specify filter conditions. 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.

Click Next: Advanced Settings to configure advanced settings.

Parameter	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	The environment tag that is used to identify the DTS instance. You can select an environment tag based on your business requirements. In this example, no environment tag is selected.
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.

Optional. In the lower part of the page, click Next: Configure Database and Table Fields. In the dialog box that appears, specify Primary Key Column, Distribution Key, and Engine for the tables that you want to migrate.
Note
- This step is available only if you select Schema Migration for the Migration Types parameter. You can set the Definition Status parameter to All and modify the database and table fields.
- You can select multiple columns for the Primary Key Column parameter from the drop-down list. One or more columns specified for the Primary Key Column parameter can be selected for the Distribution Key parameter.
- If the table does not have primary keys or UNIQUE constraints, select duplicate for the Engine parameter. Otherwise, the data migration task may fail or data loss may occur.

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 an 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.

Data type mappings

Category	Data type in ApsaraDB RDS for MySQL	Data type in ApsaraDB for SelectDB
Numeric	TINYINT	TINYINT
	TINYINT UNSIGNED	SMALLINT
	SMALLINT	SMALLINT
	SMALLINT UNSIGNED	INT
	MEDIUMINT	INT
	MEDIUMINT UNSIGNED	BIGINT
	INT	INT
	INT UNSIGNED	BIGINT
	BIGINT	BIGINT
	BIGINT UNSIGNED	LARGEINT
	BIT(M)	INT
	Decimal	Decimal Note ZEROFILL is not supported.
	Numeric	Decimal
	Float	Float
	Double	DOUBLE
	BOOL BOOLEAN	BOOLEAN
DATE AND TIME	DATE	DATEV2
	DATETIME[(fsp)]	DATETIMEV2
	Timestamp[(fsp)]	DATETIMEV2
	Time[(fsp)]	VARCHAR
	YEAR[(4)]	INT
STRING	CHAR VARCHAR	VARCHAR Important To avoid data loss, data of the CHAR and VARCHAR(n) types is converted to VARCHAR(4*n) after the data is migrated to the destination ApsaraDB for SelectDB instance. If you do not specify the length of data, the default value VARCHAR(65533) is used. Data with a length of more than 65,533 characters is converted to the STRING type after it is migrated to the destination ApsaraDB for SelectDB instance.
	BINARY VARBINARY	STRING
	TINYTEXT TEXT MEDIUMTEXT LONGTEXT	STRING
	TINYBLOB BLOB MEDIUMBOLB LONGBLOB	STRING
	ENUM	STRING
	SET	STRING
	JSON	STRING

Additional columns