How to migrate data from an ApsaraDB RDS for MySQL instance on RDS Enterprise Edition to an ApsaraDB RDS for MySQL instance on Cluster Edition - Data Transmission Service

This topic describes how to use Data Transmission Service (DTS) to migrate data from an ApsaraDB RDS for MySQL instance on RDS Enterprise Edition to an ApsaraDB RDS for MySQL instance on Cluster Edition.

Prerequisites

The source and destination ApsaraDB RDS for MySQL instances are created. For more information, see Create an ApsaraDB RDS for MySQL instance.
The storage space of the destination ApsaraDB RDS for MySQL instance on Cluster Edition must be larger than the storage space used by the source ApsaraDB RDS for MySQL instance on RDS Enterprise Edition.

Notes

Note

During schema migration, DTS migrates foreign keys from the source database to the destination database.
During full data migration and incremental data migration, DTS temporarily disables the constraint check and cascade operations on foreign keys at the session level. If you perform the cascade update and delete operations on the source database during data migration, data inconsistency may occur.

Type	Description
Source database limits	Bandwidth: The server that hosts the source database must have sufficient outbound bandwidth. Otherwise, the data migration speed is affected. The tables to be migrated must have primary keys or UNIQUE constraints, and the fields must be unique. Otherwise, duplicate data may exist in the destination database. If you migrate data at the table level and need to edit objects, such as mapping table or column names, a single data migration task can migrate a maximum of 1,000 tables. If the number of tables exceeds the limit, an error is reported after you submit the task. In this case, split the tables into multiple migration tasks or configure a migration task for 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 migration, do not perform DDL operations to change the schema of the databases or tables. Otherwise, the data migration task fails. Note During full 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 ensure 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	We recommend that you use the same MySQL version for the source and destination databases to ensure compatibility. DTS does not migrate data where a parser defined by using comments is used. If online DDL changes are made in temporary table mode in the source database, including but not limited to merging multiple tables, data loss may occur in the destination database or the migration instance may fail. If the destination database is MySQL database 8.0.23 or later, and the columns to receive data include invisible columns, the destination columns to which the data is written cannot be found. In this case, the DTS instance fails to run 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. If you do not use the schema migration feature of DTS, you must ensure the compatibility of fields. Otherwise, the instance may fail or data loss may occur. For example, if a field in the source table is of the `text` type and the destination field is of the `varchar(255)` type, data truncation may occur if the source table contains large objects. If the data to be migrated contains information such as rare characters or emojis that takes up four bytes, the destination databases and tables to receive the data must use UTF8mb4 character set. Note If you use the schema migration feature of DTS, set the instance parameter `character_set_server` in the destination database to UTF8mb4 character set. DTS executes the CREATE DATABASE IF NOT EXISTS `test` statement in the source database as scheduled to move forward the binary log file position. Before you migrate data, evaluate the performance of the source and destination databases. We recommend that you migrate data during off-peak hours. This is because DTS consumes read and write resources of the source and destination databases during full data migration, which may increase the database load. During full data migration, INSERT statements are run concurrently. This causes table fragmentation in the destination database. After full data migration is complete, the storage space used by the tables in the destination database is larger than that used by the tables in the source instance. Confirm whether the migration precision for columns of the FLOAT or DOUBLE data type meets your business requirements. DTS reads the values of these columns using `ROUND(COLUMN,PRECISION)`. If the precision is not specified, DTS migrates FLOAT values with a precision of 38 digits and DOUBLE values with a precision of 308 digits. DTS attempts to resume failed migration tasks within seven days. Before you switch your workloads to the destination instance, you must stop or release the task, or run the `revoke` command to revoke the write permissions of the account that DTS uses to access the destination instance. This prevents the source data from overwriting the data in the destination instance after the task is automatically resumed. DTS automatically creates a database in ApsaraDB RDS for MySQL. If the name of the database to be migrated does not comply with the naming conventions of ApsaraDB RDS for MySQL, you must create a database in ApsaraDB RDS for MySQL before you configure the migration task. For more information, see Manage databases. If DDL statements fail to be executed in the destination database, the DTS task continues to run. You can view the DDL statements that fail to be executed in task logs. For more information about how to view task logs, see View task logs. If you write column names that differ only in capitalization to the same table in the destination MySQL database, the data migration result may not meet your expectations because the column names in MySQL databases are not case-sensitive. After data migration is complete, that is, the Status of the instance changes to Completed, we recommend that you run the `analyze table <table name>` command to check whether data is written to the destination table. For example, if a high-availability (HA) switchover is triggered in the destination MySQL database, data may be written only to the memory. As a result, data loss occurs. 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 you want to migrate accounts from the source database to the destination database, you need to learn the prerequisites and precautions. For more information, see Migrate database accounts. 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.

Billing

Migration type	Instance configuration fee	Internet traffic fee
Schema migration and full data migration	Free of charge.	When the Access Method parameter of the destination database is set to Public IP Address, you are charged for Internet traffic. For more information, see Billing overview.
Incremental data migration	Charged. For more information, see Billing overview.

Migration types

Schema migration
Data Transmission Service (DTS) migrates the schemas of the selected objects from the source database to the destination database.
Note
- DTS supports schema migration for the following types of objects: tables, views, triggers, stored procedures, and stored functions.
  Note
  The routine_body of the stored procedure, routine_body of the stored functions, and select_statement of the views cannot be modified during the migration.
- During schema migration, DTS changes the value of the SECURITY attribute from DEFINER to INVOKER for views, stored procedures, and functions. In addition, DTS sets the DEFINER to the destination database account used in the migration.
  Note
  The SECURITY attribute and DEFINER cannot be modified during the migration.
- DTS does not migrate user information. To call a view, stored procedure, or stored function of the destination database, you must grant the read and write permissions to INVOKER.
Full data migration
DTS migrates the historical data of required objects from the source database to the destination database.
Incremental data migration
After full data migration is complete, DTS migrates incremental data from the source database to the destination database. Incremental data migration allows data to be migrated smoothly without interrupting the services of self-managed applications during data migration.

Supported SQL operations for incremental migration

Operation type	SQL statement
DML	INSERT, UPDATE, and DELETE
DDL	ALTER TABLE and ALTER VIEW CREATE FUNCTION, CREATE INDEX, CREATE PROCEDURE, CREATE TABLE, and CREATE VIEW DROP INDEX and DROP TABLE RENAME TABLE Important RENAME TABLE operations may cause data inconsistency between the source and destination databases. For example, if you select a table as the object to be migrated and rename the table during data migration, the data of this table is not migrated to the destination database. To prevent this situation, you can select the database to which this table belongs as the object to be migrated when you configure the data migration task. Make sure that the databases to which the table belongs before and after the RENAME TABLE operation are added to the objects to be migrated. TRUNCATE TABLE

Permissions for database accounts

Database	Schema migration	Full migration	Incremental migration
Source ApsaraDB RDS for MySQL instance on RDS Enterprise Edition	SELECT permission	SELECT permission	Read and write
Destination ApsaraDB RDS for MySQL instance on Cluster Edition	Read and write	Read and write	Read and write

To create and grant permissions to a database account, see Create an account and Modify the permissions of an account.

Note

If you do not create and grant permissions to the database account in the ApsaraDB RDS for MySQL console, you must ensure that the account has the REPLICATION CLIENT, REPLICATION SLAVE, SHOW VIEW, and SELECT permissions.
To migrate account information from the source database, the database account used for the task configuration requires additional permissions. For more information, see Migrate database accounts.

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.

Warning

After you configure the source and destination databases, we recommend that you read the Limits that are displayed in the upper part of the page. Otherwise, the task may fail or data inconsistency may occur.

Category	Configuration	Description
None	Task Name	The name of the DTS task. DTS automatically generates a task name. We recommend that you specify an informative name that makes it easy to identify the task. You do not need to specify a unique task name.
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 ApsaraDB RDS for MySQL instance resides.
	Replicate Data Across Alibaba Cloud Accounts	In this example, data is migrated between instances under the same Alibaba Cloud account. Select No.
	RDS Instance ID	Select the ID of the source ApsaraDB RDS for MySQL instance.
	Database Account	Enter the database account of the source ApsaraDB RDS for MySQL instance. For more information about the permission requirements, see Permissions 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 MySQL.
	Access Method	Select Cloud Instance.
	Instance Region	Select the region where the destination ApsaraDB RDS for MySQL instance resides.
	Replicate Data Across Alibaba Cloud Accounts	In this example, data is migrated between instances under the same Alibaba Cloud account. Select No.
	RDS Instance ID	Select the ID of the destination ApsaraDB RDS for MySQL instance.
	Database Account	Enter the database account of the destination RDS instance. For more information about the permission requirements, see Permissions 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.

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.

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.
Method to Migrate Triggers in Source Database	Select a method to migrate triggers based on your requirements. If the objects to be migrated do not involve triggers, you do not need to configure this parameter. For more information, see Configure the method to synchronize or migrate triggers. Note This parameter is available only when you select both Schema Migration and Incremental Data Migration for Migration Types.
Enable Migration Assessment	This feature evaluates whether the schemas of the source and destination databases meet the requirements. The evaluation covers items such as index length, stored procedures, and dependent tables. You can select Yes or No based on your requirements. Note This parameter is available only when you select Schema Migration for Migration Types. If you select Yes, the precheck duration may increase. You can view the Assessment Result during the precheck. The evaluation result does not affect the precheck result.
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.
Whether to migrate Event	Specifies whether to migrate events from the source database. If you select Yes, you must complete the subsequent operations. For more information, see Synchronize or migrate events.
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 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.
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 If you use the object name mapping feature, the migration of other objects that depend on the mapped object may fail. To filter data using a WHERE clause, right-click the table that you want to migrate in the Selected Objects box and set the filter condition in the dialog box that appears. For more information about how to set the filter condition, see Set a filter condition. To select DML or DDL operations for incremental migration at the database or table level, right-click the migration object in the Selected Objects box and select the required DML and DDL operations in the dialog box that appears.

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.
Copy the temporary table of the Online DDL tool that is generated in the source table to the destination database.	If you use DMS or the gh-ost tool to perform online DDL operations on the source database, you can specify whether to migrate the data of temporary tables generated by online DDL operations. Valid values: Important You cannot use tools such as pt-online-schema-change to perform online DDL operations on the source database. Otherwise, the DTS task fails. 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, Adapt to DMS Online DDL: DTS does not migrate the data of temporary tables generated by online DDL operations. Only the original DDL operations that are performed by using DMS are migrated. Note If you select this option, the tables in the destination database may be locked. No, Adapt to gh-ost: DTS does not migrate the data of temporary tables generated by online DDL operations. Only the original DDL operations that are performed by using the gh-ost tool are migrated. You can use the default or custom regular expressions to filter out the shadow tables of the gh-ost tool and tables that are not required. Note If you select this option, the tables in the destination database may be locked.
Whether to Migrate Accounts	Select whether to migrate account information from the source database based on your requirements. If you select Yes, you must also select the accounts that you want to migrate and confirm their permissions.
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 based on your requirements. In this example, no selection is needed.
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.

Click Next Step: Data Verification to configure the data verification task.
For more information about how to use the data verification feature, see Configure a data verification task.

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.