Migrate data between ApsaraDB RDS for MariaDB instances-Data Transmission Service(DTS)-阿里云帮助中心

Prerequisites

Create a destination ApsaraDB RDS for MariaDB instance. For more information, see Create an ApsaraDB RDS for MariaDB instance.
The destination ApsaraDB RDS for MariaDB instance must have more available storage space than the source ApsaraDB RDS for MariaDB instance uses.

Limits

Note

During schema migration, DTS migrates foreign keys from the source database to the destination database.
During full and incremental data migration, DTS temporarily disables constraint checks and foreign key cascading operations at the session level. If cascading updates or deletes occur in the source database while the task is running, data inconsistency may occur.

Type	Description
Source database limits	The server that hosts the source database must have sufficient outbound bandwidth. Otherwise, the migration speed is reduced. Tables to be migrated must have a primary key or a unique constraint, and the fields in the constraint must contain unique values. Otherwise, duplicate data may exist in the destination database. If you migrate data at the table level and need to edit the objects, such as mapping table or column names, a single migration task supports a maximum of 1,000 tables. If you exceed this limit, you will receive a request error when you submit the task. To work around this, we recommend that you split the tables into multiple migration tasks or configure a task to migrate the entire database. If you perform incremental data migration, the binary log must meet the following requirements: The binary log feature must be enabled, with `binlog_format` set to `ROW` and `binlog_row_image` set to `FULL`. Otherwise, the precheck fails and the data migration task cannot start. If you perform only an incremental data migration task, the local binary logs of the source database must be retained for more than 24 hours. If you perform a task that includes both full and incremental data migration, the binary logs must be retained for at least 7 days. You can change the retention period to more than 24 hours after the full data migration is complete. If the retention period is too short, DTS may be unable to obtain the binary logs. This can cause the task to fail or, in extreme cases, lead to data loss or inconsistency. The DTS SLA does not cover issues caused by an insufficient binary log retention period. During the schema migration and full migration phases, do not perform DDL operations that change the database or table schema. Otherwise, the data migration task will fail. Note During the full migration phase, DTS queries the source database. This creates a metadata lock, which may block DDL operations on the source database. If you perform only a full data migration, do not write new data to the source database. Otherwise, data inconsistency will occur between the source and destination databases. To maintain real-time data consistency, select schema migration, full data migration, and incremental data migration.
Other limits	Evaluate the performance of the source and destination databases before you start. We recommend migrating during off-peak hours. During full data migration, DTS consumes read and write resources on both the source and destination databases, which may increase their server load. During full data migration, concurrent `INSERT` operations cause table fragmentation in the destination database. After the migration is complete, the tables in the destination database use more storage space than those in the source instance. Confirm that the migration precision for `FLOAT` or `DOUBLE` columns meets your business requirements. DTS reads values from these columns by using the `ROUND(COLUMN,PRECISION)` function. If you do not specify the precision, DTS uses a precision of 38 digits for `FLOAT` columns and 308 digits for `DOUBLE` columns. DTS attempts to resume failed migration tasks within seven days. Before you switch your business to the destination instance, make sure to stop or release the task. Alternatively, use the `REVOKE` command to revoke the write permissions of the account that DTS uses to access the destination instance. This prevents the resumed task from overwriting data in the destination instance. If a DDL statement fails to write to the destination database, the DTS task continues to run. You must view the failed DDL statement in the task logs. For more information, see Query task logs. Ensure that no invisible columns exist in the tables to be migrated in the source database or in the destination tables. Otherwise, the DTS instance may fail or cause data loss. If a task fails, DTS support staff will attempt to restore it within eight hours. During restoration, they may restart the task or adjust its parameters. Note Only DTS task parameters are modified—not database parameters. Parameters that may be adjusted include those listed in Modify instance parameters.
Special cases	If the destination database is an ApsaraDB RDS for MariaDB instance DTS automatically creates a database in the ApsaraDB RDS for MariaDB instance. However, if a database name does not comply with ApsaraDB RDS for MariaDB naming conventions, you must create that database in the destination instance before you configure the migration task. For more information, see Create a database and an account.

Billing

Migration type	Link configuration fee
Full data migration	Free of charge.
Incremental data migration	Charged. For more information, see Billing overview.

Migration types

Schema migration

DTS migrates the schemas of the selected objects from the source database to the destination database.
Full data migration

DTS migrates all existing data from the selected objects in the source database to the destination database.
Incremental data migration

After the full migration is complete, DTS migrates incremental data changes from the source database to the destination database. This helps you complete the migration with minimal downtime.

SQL operations supported for incremental migration

Operation type	SQL statement
DML	INSERT, UPDATE, DELETE
DDL	ALTER TABLE, ALTER VIEW CREATE FUNCTION, CREATE INDEX, CREATE PROCEDURE, CREATE TABLE, CREATE VIEW DROP INDEX, DROP TABLE RENAME TABLE Important A RENAME TABLE operation may cause data inconsistency. For example, if you select only one table as the migration object and rename the table in the source instance during migration, the data of this table is not migrated to the destination database. To prevent this issue, select the entire database to which the table belongs as the migration object 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 both included in the migration objects. TRUNCATE TABLE

Permissions required for database accounts

Database	Schema migration	Full data migration	Incremental data migration
Source ApsaraDB RDS for MariaDB instance	SELECT permission	SELECT permission	Read and write permissions
Destination ApsaraDB RDS for MariaDB 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 in an ApsaraDB RDS for MariaDB instance, see Create an account and Modify or reset account permissions.

Procedure

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

Note
The actual operations may vary based on the mode and layout of the DMS console. For more information, see Simple mode console and Customize the layout and style of the DMS console.
1. Log on to the Data Management (DMS) console.
2. In the top menu bar, choose Data + AI > Data Transmission (DTS) > Data Migration.
3. To the right of Data Migration Tasks, select the region where the migration instance is located.
Click Create Task to navigate to the task configuration page.
Optional: In the upper-right corner of the page, click New Configuration Page.
Note
- If you are already on the new configuration page (the button in the upper-right corner is Back to Previous Version), you can skip this step.
- The parameters on the new and old configuration pages are different. We recommend that you use the new configuration page.

Configure the source and destination databases.

Category	Parameter	Description
N/A	Task Name	DTS automatically generates a task name. We recommend using a descriptive name for easy identification. The name does not need to be unique.
Source Database	Select Existing Connection	To use a database instance that has been added to the system (created or saved), select the desired database instance from the drop-down list. The database information below will be automatically configured. Note In the DMS console, this parameter is named Select a DMS database instance.. If you have not registered the database instance with the system, or do not need to use a registered instance, manually configure the database information below.
	Database Type	Select MariaDB.
	Connection Type	Select Alibaba Cloud Instance.
	Instance Region	Select the region where the source ApsaraDB RDS for MariaDB instance resides.
	Cross-account	This topic describes how to migrate data within the same Alibaba Cloud account. Select No.
	Instance ID	Select the ID of the source ApsaraDB RDS for MariaDB instance.
	Database Account	Enter the database account of the source ApsaraDB RDS for MariaDB instance. For information about the required permissions, see Permissions required for database accounts.
	Database Password	Enter the password for the database account.
	Connection Method	The default setting for ApsaraDB RDS for MariaDB instances is Non-encrypted.
Destination Database	Select Existing Connection	To use a database instance that has been added to the system (created or saved), select the desired database instance from the drop-down list. The database information below will be automatically configured. Note In the DMS console, this parameter is named Select a DMS database instance.. If you have not registered the database instance with the system, or do not need to use a registered instance, manually configure the database information below.
	Database Type	Select MariaDB.
	Connection Type	Select Alibaba Cloud Instance.
	Instance Region	Select the region where the destination ApsaraDB RDS for MariaDB instance resides.
	RDS Instance ID	Select the ID of the destination ApsaraDB RDS for MariaDB instance.
	Database Account	Enter the database account of the destination ApsaraDB RDS for MariaDB instance.
	Database Password	Enter the password for the database account.
	Connection Method	The default setting for ApsaraDB RDS for MariaDB instances is Non-encrypted.

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

Configure the task objects.

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

Parameter	Description
Migration Types	If you only need to perform a full migration, select both Schema Migration and Full Data Migration. To perform a migration with no downtime, select Schema Migration, Full Data Migration, and Incremental Data Migration. Note If you do not select Schema Migration, you must ensure that a database and tables to receive the data exist in the destination database. You can also use the object name mapping feature in the Selected Objects box as needed. If you do not select Incremental Data Migration, do not write new data to the source instance during data migration to ensure data consistency.
Method to Migrate Triggers in Source Database	Select a method to migrate triggers based on your business requirements. If no triggers are to be migrated, you do not need to configure this parameter. For more information, see Configure how to synchronize or migrate triggers. Note This parameter is available only if you select Schema Migration for Migration Types.
Processing Mode for Existing Destination Tables	Precheck and Report Errors: Checks whether tables with the same names exist in the destination database. If no tables with the same names exist, the precheck is passed. If tables with the same names exist, an error is reported during the precheck, and the data migration task does not start. Note If a table in the destination database has the same name but cannot be easily deleted or renamed, you can change the name of the table in the destination database. For more information, see Object name mapping. Ignore Errors and Proceed: Skips the check for tables with the same names. Warning Selecting Ignore Errors and Proceed may cause data inconsistency and business risks. For example: If the table schemas are consistent and a record in the destination database has the same primary key value as a record in the source database: During full migration, DTS keeps the record in the destination database. The record from the source database is not migrated. During incremental migration, DTS does not keep the record in the destination database. The record from the source database overwrites the record in the destination database. If the table schemas are inconsistent, only some columns of data may be migrated, or the migration may fail. Proceed with caution.
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 granularity for selecting migration objects is database, table, and column. If you select only tables or columns as migration objects, other objects such as views, triggers, and stored procedures are not migrated to the destination database.
Selected Objects	To change the name of a single migration object in the target instance, right-click the object in the Selected Objects box. For more information, see Map individual schema, table, and column names. To change the names of multiple migration objects in the target instance, click Selected Objects in the upper-right corner of the Batch Edit box. For more information, see Map multiple schema, table, and column names. Note If you use the object name mapping feature, the migration of other objects that depend on a renamed object may fail. To specify a WHERE clause to filter data, right-click a table in the Selected Objects section and specify the filter condition in the dialog box that appears. For more information, see Set filter conditions. To select SQL operations to migrate at the database or table level, right-click an object in the Selected Objects section and select the desired SQL operations in the dialog box that appears.

Click Next: Advanced Settings to configure advanced parameters.

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

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

Purchase an instance.

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

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

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

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

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