This topic describes how to migrate data from an ApsaraDB RDS for MariaDB TX instance to an ApsaraDB RDS for MySQL instance by using Data Transmission Service (DTS). DTS supports schema migration, full data migration, and incremental data migration. When you configure a data migration task, you can select all the supported migration types to ensure service continuity.
Prerequisites
An ApsaraDB RDS for MySQL instance is created. For more information, see Create an ApsaraDB RDS for MySQL instance.
The available storage space of the ApsaraDB RDS for MySQL instance must be larger than the total size of the data in the ApsaraDB RDS for MariaDB TX instance.
Precautions
DTS uses read and write resources of the source and destination databases during full data migration. This may increase the loads of the database servers. If the database performance is unfavorable, the specification is low, or the data volume is large, database services may become unavailable. For example, DTS occupies a large amount of read and write resources in the following cases: a large number of slow SQL queries are performed on the source database, the tables have no primary keys, or a deadlock occurs in the destination database. Before you migrate data, evaluate the impact of data migration on the performance of the source and destination databases. We recommend that you migrate data during off-peak hours. For example, you can migrate data when the CPU utilization of the source and destination databases is less than 30%.
The tables to be migrated in the source database must have PRIMARY KEY or UNIQUE constraints and all fields must be unique. Otherwise, the destination database may contain duplicate data records.
If a data migration task fails, DTS automatically resumes the task. Before you switch your workloads to the destination instance, stop or release the data migration task. Otherwise, the data in the source instance will overwrite the data in the destination instance after the task is resumed.
Billing rules
Migration type | Task configuration fee | Internet traffic fee |
Schema migration and full data migration | Free of charge. | Charged only when data is migrated 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 schemas of required objects to the destination database. DTS supports schema migration for the following types of objects: table, view, trigger, stored procedure, and function. DTS does not support schema migration for events.
NoteDuring schema migration, DTS changes the value of the SECURITY attribute from DEFINER to INVOKER for views, stored procedures, and functions.
DTS does not migrate user information. To call a view, stored procedure, or function of the destination database, you must grant read and write permissions to INVOKER.
Full data migration
DTS migrates the historical data of required objects to the destination database.
NoteDuring full data migration, concurrent INSERT operations cause fragmentation in the tables of the destination database. After full data migration is complete, the size of used tablespace of the destination database is larger than that of the source database.
To ensure successful data migration, we recommend that you do not perform DDL operations on the source database during full data migration.
Incremental data migration
After full data migration is complete, DTS retrieves binary log files from the source database, and migrates incremental data to the destination database in real time.
SQL operations that can be synchronized during incremental data migration
Operation type | SQL statement |
DML | INSERT, UPDATE, DELETE, and REPLACE |
DDL |
|
Permissions required for database accounts
Database | Schema migration | Full data migration | Incremental data migration |
ApsaraDB RDS for MariaDB TX instance | The SELECT permission | The SELECT permission | The REPLICATION CLIENT, REPLICATION SLAVE, SHOW VIEW, and SELECT permissions |
ApsaraDB RDS for MySQL instance | Read and write permissions | Read and write permissions | Read and write permissions |
For information about how to create a database account and grant permissions to the account, see the following topics:
ApsaraDB RDS for MariaDB TX instance: See Create an account on an ApsaraDB RDS for MariaDB TX instance.
ApsaraDB RDS for MySQL instance: See Create an account on an ApsaraDB RDS for MySQL instance and Modify the permissions of a standard account for an ApsaraDB RDS for MySQL instance.
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
Log on to the DTS console.
In the left-side navigation pane, click Data Migration.
In the upper-left corner of the page, select the region in which the data migration instance resides.
DMS console
NoteThe 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.
Log on to the DMS console.
In the top navigation bar, move the pointer over .
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.
WarningAfter 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.
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
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.
NoteIn 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 MariaDB.
Access Method
Select Alibaba Cloud Instance.
Instance Region
Select the region where the source ApsaraDB RDS for MariaDB TX instance resides.
Replicate Data Across Alibaba Cloud Accounts
In this example, the migration is between instances that belong to the same Alibaba Cloud account. Select No.
Instance ID
Select the ID of the source ApsaraDB RDS for MariaDB TX instance.
Database Account
Enter the database account of the source ApsaraDB RDS for MariaDB TX instance. For information about the permissions that are required for the account, see Permissions required for database accounts.
Database Password
The password that is used to access the database.
Encryption
Select Non-encrypted.
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.
NoteIn 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 Alibaba 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, the migration is between instances that belong to 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 ApsaraDB RDS for MySQL instance. For information about the permissions that are required for the account, 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 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.
In the lower part of the page, click Test Connectivity and Proceed.
NoteMake 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 Schema Migration and Full Data Migration.
To ensure service continuity during data migration, select Schema Migration, Full Data Migration, and Incremental Data Migration.
NoteIf 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
The method that is used to migrate triggers from the source database. You can select a migration method based on your business requirements. If no triggers are involved, you do not need to configure this parameter. For more information, see Configure the method to synchronize or migrate triggers.
NoteYou can configure this parameter only when you select both Migration Types and Schema Migration and Incremental Data Migration.
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.
NoteIf 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.
WarningIf 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.
Source Objects
Select one or more objects from the Source Objects section. Click the
icon to add the objects to the Selected Objects section. NoteYou 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.
NoteIf you use the object name mapping feature, other objects that depend on the renamed objects may fail to be migrated.
To configure a filter condition to filter data, right-click the table that you want to migrate in the Selected Objects section. In the dialog box that appears, configure a filter condition. For more information, see Configure SQL conditions to filter data.
To select the DML or DDL operations that you want to migrate at the database or table level during incremental data migration, right-click the objects that you want to migrate in the Selected Objects section. In the dialog box that appears, select the DML and DDL operations that you want to migrate.
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.
NoteIf 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.
ImportantThe 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.
NoteYou 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.
NoteYou 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, you do not need to select an environment tag.
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.
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.
NoteBefore 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?
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.
NoteIf 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.
What to do next
The database accounts that are used for data migration have read and write permissions. After data migration is complete, you must delete the database accounts of both the ApsaraDB RDS for MariaDB TX and ApsaraDB RDS for MySQL instances to ensure database security.